RARE DISEASE
Severe combined immunodeficiency due to adenosine deaminase deficiency
Severe combined immunodeficiency due to adenosine deaminase deficiency
Severe combined immunodeficiency due to adenosine deaminase deficiency
Synonyms: ADA deficiency, SCID due to adenosine deaminase deficiency
Synonyms: ADA deficiency, SCID due to adenosine deaminase deficiency
Synonyms: ADA deficiency, SCID due to adenosine deaminase deficiency
Drug discovery
6
drugs
With orphan designations
Overview
Severe combined immunodeficiency due to adenosine deaminase deficiency (ADA-SCID) is an autosomal recessive disorder caused by ADA gene mutations (20q13.11), leading to toxic purine metabolite accumulation, profound lymphopenia (T-, B-, NK-cell deficiency), and life-threatening infections. Patients may present with systemic manifestations, including neurodevelopmental deficits, skeletal abnormalities, and pulmonary alveolar proteinosis. Diagnosis involves low ADA activity, elevated dATP, and genetic testing. Untreated cases are typically fatal by age 2 [1][2][9].
Burden
Untreated: Mortality approaches 100% by age 2 due to opportunistic infections [4][19].
Survivors face risks of neurodevelopmental delays, chronic pulmonary disease, and malignancy [9][15].
High healthcare costs from ERT, HSCT complications, and long-term multidisciplinary care [9][16].
Early diagnosis via newborn screening improves outcomes significantly [14].
Therapies
Enzyme replacement therapy (ERT): Stabilizes patients with PEG-ADA but requires lifelong administration and offers incomplete immunity [8][17].
Hematopoietic stem cell transplantation (HSCT): Curative, with 72–86% 5-year survival for matched sibling donors but lower success with mismatched donors [2][16].
Gene therapy: Autologous CD34+ cell transplantation with ADA-corrected vectors achieves >90% 5-year survival and sustained immune reconstitution [3][12][16].
Categories: rare genetic diseases, rare immunological diseases, rare inborn errors of metabolism, rare transplant-related disorders
Research Papers
484 drug discovery papers about Severe combined immunodeficiency due to adenosine deaminase deficiency, with 2 first-in-class and 1 next-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
484 drug discovery papers about Severe combined immunodeficiency due to adenosine deaminase deficiency, with 2 first-in-class and 1 next-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
categories:
Small molecules
small molecules
2025-07-01 | Synthetic approaches and biological functions of 2 deoxyadenosine: A review of nucleoside chemistry and cellular dynamics
2′ Deoxyadenosine (dAdo) resides at the critical junction of de novo and salvage deoxyribonucleotide synthesis while salvage phosphorylation of dAdo replenishes the dATP-pool, the de novo pathway via ribonucleotide reductase (RNR) generates dNTPs from ribonucleotides. Disruption of this balance as typified in adenosine deaminase (ADA) deficiency causes intracellular dAdo and dATP accumulation, potent RNR inhibition, dNTP‐pool disruption and replication stress. Concurrently, synthetic modification of the dAdo scaffold has driven the development of analogues that exploit nucleoside transporters, resist deaminative inactivation and selectively accumulate in target cells to modulate DNA repair, immune signalling and mitochondrial DNA maintenance. This review presents a unified account of dAdo’s structural and molecular properties, its role in dNTP homeostasis and cellular dynamics, the pathological consequences of salvage/de novo dysregulation, and the latest synthetic and medicinal chemistry strategies built on the dAdo framework.
2025-06-27 | Adenosine and Adenosine Deaminase Contrary Manifestations in Immunity.
Adenosine (Ado) is an important purine that regulates numerous physiological functions. Adenosine deaminase (ADA) catalyses the irreversible deamination of Ado and its derivatives. Ado and ADA are the essential players in the immune system, but their roles often are opposite, mutually exclusive and competitive. This work presents several critical immune system situations demonstrating the conflicts between the functions of Ado and ADA. Ado suppresses immunity and inflammation by inhibiting lymphocyte proliferation. ADA supports the development of the immune system by metabolising Ado. In infectious and inflamed diseases, the increased ADA levels in tissue exudates decrease Ado concentration, aggravating inflammation. ADA inhibition is required to protect Ado and mitigate inflammation. In hereditary ADA deficiency, cytotoxic metabolites of Ado accumulate in lymphocytes and suppress immunity. ADA deficiency became the second cause of severe combined immunodeficiency (SCID). Enzyme replacement therapy using PEGylated ADA and ADA gene therapy are recognised in ADA-SCID treatment. The human immunodeficiency virus (HIV) hyperactivates host immune cells, resulting in super-inflammation and acquired immunodeficiency syndrome (AIDS). Cytotoxic derivatives of Ado suppress HIV-1 growth, whereas ADA inactivates cytotoxic nucleosides. ADA inhibition is required to prolong the elimination time and reduce the effective doses of anti-AIDS drugs. Ado levels elevate in the tumour microenvironment, promote immunity suppression and condition tumour cell evasion of immune surveillance. ADA neutralises Ado and restores immunity. Furthermore, ADA can simultaneously bind to the CD26 protein on lymphocytes and the A2AR receptors on antigen-presenting dendritic cells. Created CD26-ADA-A2AR complex bridges T and dendritic cells, stimulating T lymphocyte function.
2023-08-11 | Computational 3D structure prediction followed by molecular docking to reveal the novel drug targets against ADA
Adenosine deaminase (ADA) is a functional enzyme that transforms deoxyadenosine and adenosine into deoxyinosine and inosine respectively. ADA deficiency causes toxic purine degradation byproducts to build up in the body, which has a particularly negative impact on lymphocytes and results in adenosine deaminase-deficient severe combined immunodeficiency. Different in silico techniques including threading, ab initio and homology modeling for 3D structure prediction were applied for the prediction of ADA structures. Following the three-dimensional structure prediction analyses, an extensive computational assessment of all predicted structures for reliability was performed. The overall quality factor of the predicted ADA structures was observed 62.45% in the predicted 3D models. A Ramachandran plot was created, and 94.80% of the residues were found in the allowed and favored regions of the protein structure plot. The molecular docking analyses were performed in order to identify the potential therapeutic medication targets against ADA. The virtually examined molecules through a virtually high throughput screening may have the ability the regulation the ADA activity. The least binding energy was calculated through the molecular docking analyses and the energy values were observed -8.7 Kcal/mol. The binding residues (Lys-367, Glu-424, Asp-422, Phe-381, Ile-377, Ser-430 and Glu-374) were conserved in all the interactional analyses of the docked complexes. Finding the effective binding domain in a protein three-dimensional structure is crucial for understanding of its structural makeup and determining its functions.
2021-04-27 | Adenosine A2B receptor: A pathogenic factor and a therapeutic target for sensorineural hearing loss.
Over 466 million people worldwide are diagnosed with hearing loss (HL). About 90% of HL cases are sensorineural HL (SNHL) with treatments limited to hearing aids and cochlear implants with no FDA-approved drugs. Intriguingly, ADA-deficient patients have been reported to have bilateral SNHL, however, its underlying cellular and molecular basis remain unknown. We report that Ada-/- mice, phenocopying ADA-deficient humans, displayed SNHL. Ada-/- mice cochlea with elevated adenosine caused substantial nerve fiber demyelination and mild hair cell loss. ADA enzyme therapy in these mice normalized cochlear adenosine levels, attenuated SNHL, and prevented demyelination. Additionally, ADA enzyme therapy rescued SNHL by restoring nerve fiber structure in Ada-/- mice post two-week drug withdrawal. Moreover, elevated cochlear adenosine in untreated mice was associated with enhanced Adora2b gene expression. Preclinically, ADORA2B-specific antagonist treatment in Ada-/- mice significantly improved HL, nerve fiber density, and myelin compaction. We also provided genetic evidence that ADORA2B is detrimental for age-related SNHL by impairing cochlear myelination in WT aged mice. Overall, understanding purinergic molecular signaling in SNHL in Ada-/- mice allows us to further discover that ADORA2B is also a pathogenic factor underlying aged-related SNHL by impairing cochlear myelination and lowering cochlear adenosine levels or blocking ADORA2B signaling are effective therapies for SNHL.
2020-12-30 | In vitro adenosine deaminase inhibitory activity of some selected plant extracts and chemical compounds
Background and Aims: Adenosine deaminase (EC 3.5.4.4, ADA) is distributed in all human tissues. It catalyses the deamination of adenosine (deoxyadenosine) to inosine (deoxyinosine) via removal of an amino group. The determination of ADAinhibition is of extreme significance in the field of fundamental research and clinical diagnosis. In our study, the effects of various plant extracts and chemicals on ADA activity were investigated. Methods: Adenosine deaminase activity was determined spectrophotometrically at 625 nm. Results: The inhibitory activities of the extracts and chemical compounds increased in a dose-dependent manner. Among the plant extracts used, lemon extract was observed to exhibit the highest ADA inhibition activity with an IC50 value of 0.05 ± 0.001 mg/mL, while quercetin had the highest ADA inhibition (IC50 value of 0.004±0.0005 mg/mL) among the chemical compounds. All plant extracts and chemical compounds showed ADA inhibition activities. Conclusion: The obtained results indicate that plant extracts and some chemical compounds examined in this study can be a potential source of novel ADA-inhibitors for therapeutics.
cell therapies
2025-11-25 | Outcomes following matched sibling donor transplantation for severe combined immunodeficiency: a report from the PIDTC
ABSTRACT: The Primary Immune Deficiency Treatment Consortium performed a retrospective analysis of 133 patients with severe combined immunodeficiency (SCID) receiving matched sibling donor (MSD) hematopoietic cell transplantation (HCT) between 1980 and 2023 at 30 North American institutions. In this largest cohort of MSD outcomes in patients with SCID to date, we examined the impact of conditioning regimen and graft-versus-host disease (GVHD) prophylaxis on survival and immune recovery. Outcomes after MSD HCT for SCID were excellent. Patients without an active infection or failure to thrive (FTT) at the time of HCT had 5-year overall survival superior to those with infection or FTT. Acute and chronic GVHD outcomes were independent of GVHD prophylaxis, conditioning regimen, SCID type, or presence of maternal engraftment. Patients without active infection at the time of HCT had superior chronic GVHD-free event-free survival vs those with infection. T-cell reconstitution at 6 months was less likely achieved with use of GVHD prophylaxis or serotherapy, and in patients with leaky SCID or Omenn syndrome. At 6 months, 1 year, and 2-5 years, T-cell reconstitution was less likely with ADA, DCLRE1C, or RAG genotype. B-cell reconstitution at 1 year and 2-5 years was negatively affected by development of grade 2 to 4 or 3 to 4 acute GVHD. Conditioning did not affect T- or B-cell reconstitution. Our data suggest omitting conditioning and GVHD prophylaxis for patients with typical SCID did not negatively affect 5-year outcomes after MSD HCT, but the data are insufficient to recommend this approach for best long-term outcomes. This trial was registered at www.clinicaltrials.gov as #NCT01186913 and #NCT01346150.
2022-06-07 | Outcomes following treatment for ADA-deficient severe combined immunodeficiency: a report from the PIDTC
Abstract Adenosine deaminase (ADA) deficiency causes ∼13% of cases of severe combined immune deficiency (SCID). Treatments include enzyme replacement therapy (ERT), hematopoietic cell transplant (HCT), and gene therapy (GT). We evaluated 131 patients with ADA-SCID diagnosed between 1982 and 2017 who were enrolled in the Primary Immune Deficiency Treatment Consortium SCID studies. Baseline clinical, immunologic, genetic characteristics, and treatment outcomes were analyzed. First definitive cellular therapy (FDCT) included 56 receiving HCT without preceding ERT (HCT); 31 HCT preceded by ERT (ERT-HCT); and 33 GT preceded by ERT (ERT-GT). Five-year event-free survival (EFS, alive, no need for further ERT or cellular therapy) was 49.5% (HCT), 73% (ERT-HCT), and 75.3% (ERT-GT; P < .01). Overall survival (OS) at 5 years after FDCT was 72.5% (HCT), 79.6% (ERT-HCT), and 100% (ERT-GT; P = .01). Five-year OS was superior for patients undergoing HCT at <3.5 months of age (91.6% vs 68% if ≥3.5 months, P = .02). Active infection at the time of HCT (regardless of ERT) decreased 5-year EFS (33.1% vs 68.2%, P < .01) and OS (64.7% vs 82.3%, P = .02). Five-year EFS (90.5%) and OS (100%) were best for matched sibling and matched family donors (MSD/MFD). For patients treated after the year 2000 and without active infection at the time of FDCT, no difference in 5-year EFS or OS was found between HCT using a variety of transplant approaches and ERT-GT. This suggests alternative donor HCT may be considered when MSD/MFD HCT and GT are not available, particularly when newborn screening identifies patients with ADA-SCID soon after birth and before the onset of infections. This trial was registered at www.clinicaltrials.gov as #NCT01186913 and #NCT01346150.
2022-03-15 | Hematopoietic Cell Transplantation for Adenosine Deaminase Severe Combined Immunodeficiency—Improved Outcomes in the Modern Era
Current treatment for adenosine deaminase (ADA)-deficient severe combined immunodeficiency (SCID) includes enzyme replacement therapy (ERT), allogeneic hematopoietic stem cell transplant (HSCT), or ex vivo corrected autologous hematopoietic stem cell gene therapy. Historic data show HSCT survival is superior using unconditioned matched sibling and family compared to matched unrelated and haploidentical donors. Recent improvement in HSCT outcomes prompted us to retrospectively examine HSCT survival and long-term graft function in ADA-SCID transplanted at our center. Thirty-three ADA-deficient patients received HSCT between 1989 and 2020, with follow-up data to January 2021. Chemotherapy conditioning regimens were defined as myeloablative (MAC-busulfan/cyclophosphamide), reduced-toxicity myeloablative (RT-MAC-treosulfan-based, since 2007), or no conditioning. Serotherapy used included alemtuzumab (with or without other conditioning agents) or antithymocyte globulin (ATG). ERT was introduced routinely in 2010 until commencement of conditioning. Median age at HSCT was 3.2 (0.8-99.8) months. Twenty-one (63.6%) received stem cells from unrelated or haploidentical donors. Seventeen (51.5%) received chemotherapy conditioning and 16 (48.5%) received alemtuzumab. Median follow-up was 7.5 (0.8-25.0) years. Overall survival (OS) and event-free survival (EFS) at 8 years were 90.9% (95% CI: 79.7-100.0%) and 79% (55-91%), respectively. OS after 2007 (n = 21) was 100% vs 75% before 2007 (n = 12) (p = 0.02). Three (9.1%) died after HSCT: two from multiorgan failure and one from unexplained encephalopathy. There were no deaths after 2007, among those who received ERT and treosulfan-based conditioning pre-HSCT. Ten (30.3%) developed acute GvDH (3 grade II, 2 grade III); no chronic GvHD was observed. In the modern era, conditioned HSCT with MUD has a favorable outcome for ADA-deficient patients.
2022-01-31 | Successful engraftment of haploidentical stem cell transplant with post-transplantation cyclophosphamide in a patient with adenosine deaminase deficiency.
SCID are characterized by an imbalance in cellular and humoral immunity. Enzyme ADA deficiency represents from 10% to 15% of the SCID. This generates diminished maturation of the cell precursors. Treatments include enzyme replacement therapy, allogenic, or autologous HSCT with gene therapy, with HSCT being of choice when an identical HLA donor exists. Male patient, without relevant family antecedents or consanguinity. The patient had multiple infections during the first months of life, evidencing low immunoglobulin levels, with absence of T and B lymphocytes, and natural killer cells. Severe combined immunodeficiencies are considered due to ADA deficiency; management was begun and is derived to our hospital. Admission at 8 months of life, with chronic malnutrition and psychomotor retardation. The HLA studies were conducted without finding an identical donor, taken to HSCT with haploidentical donor. Conditioning regimen with cyclophosphamide, fludarabine, melphalan, and thymoglobulin. This patient received prophylaxis for graft-versus-host disease with cyclophosphamide, cyclosporine, and methotrexate. A 22 months post-transplant, the patient was without immunosuppressants or immunoglobulin, without evidence of graft-versus-host disease or new infections. The ADA deficiency is an infrequent pathology that can be potentially fatal if adequate treatment is not started. Haploidentical HSCT, using post-transplantation cyclophosphamide, emerges as a viable option with which good results can be achieved and improve the quality of life in patients with no other therapeutic alternatives.
2021-10-28 | Hematopoietic cell transplantation in severe combined immunodeficiency: The SCETIDE 2006-2014 European cohort
Hematopoietic stem cell transplantation (HSCT) represents a curative treatment for patients with severe combined immunodeficiency (SCID), a group of monogenic immune disorders with an otherwise fatal outcome.We performed a comprehensive multicenter analysis of genotype-specific HSCT outcome, including detailed analysis of immune reconstitution (IR) and the predictive value for clinical outcome.HSCT outcome was studied in 338 patients with genetically confirmed SCID who underwent transplantation in 2006-2014 and who were registered in the SCETIDE registry. In a representative subgroup of 152 patients, data on IR and long-term clinical outcome were analyzed.Two-year OS was similar with matched family and unrelated donors and better than mismatched donor HSCT (P < .001). The 2-year event-free survival (EFS) was similar in matched and mismatched unrelated donor and less favorable in mismatched related donor (MMRD) HSCT (P < .001). Genetic subgroups did not differ in 2-year OS (P = .1) and EFS (P = .073). In multivariate analysis, pretransplantation infections and use of MMRDs were associated with less favorable OS and EFS. With a median follow-up of 6.2 years (range, 2.0-11.8 years), 73 of 152 patients in the IR cohort were alive and well without Ig dependency. IL-2 receptor gamma chain/Janus kinase 3/IL-7 receptor-deficient SCID, myeloablative conditioning, matched donor HSCT, and naive CD4 T lymphocytes >0.5 × 10e3/μL at +1 year were identified as independent predictors of favorable clinical and immunologic outcome.Recent advances in HSCT in SCID patients have resulted in improved OS and EFS in all genotypes and donor types. To achieve a favorable long-term outcome, treatment strategies should aim for optimal naive CD4 T lymphocyte regeneration.
gene therapies
2025-06-04 | Quantifying the mutational landscape of retroviral and lentiviral vectors in gene therapy patients.
Adenosine deaminase severe combined immunodeficiency (ADA-SCID) is a monogenic disorder caused by mutations in the ADA gene. Gene therapy using γ-retroviral and lentiviral vector gene addition approaches have shown curative results. We sequenced the ADA transgene in transduced CD3+ T cells, and in peripheral blood cells from patients treated with autologous CD34+ cells transduced with either a γ-retroviral or lentiviral ADA gene vector to assess transgene mutational profiles. In both CD3+ T cells and ADA-SCID patients' cells treated with the lentiviral vector, we observed significantly higher occurrences of guanine (G)-to-adenosine (A) base substitutions than with the γ-retroviral vector. We hypothesized that this G-to-A mutational signature was due to the APOBEC3 cytosine deaminase protein family. By knocking out APOBEC3 genes in HEK239T packaging cells, APOBEC3-mediated mutagenesis decreased by 91.2% along the transgene in CD34+ transduced cells in comparison to CD34+ cells transduced with lentiviral supernatant packaged in parental HEK293T cells.
2025-04-15 | Gene Therapy in Rare Disorders
Gene therapy -- the delivery of therapeutic nucleic acids (DNA; RNA; oligonucleotides) to correct, silence, or replacedisease-causing genetic alterations -- has achieved its most transformative clinical results in rare monogenic disorderswhere a single gene defect causes a well-defined, severe, and progressive disease amenable to genetic correction. Thepast decade has seen 18 gene therapy marketing authorisations in the EU (2012-2025), with the pace accelerating from1-2 approvals per year (2015-2018) to 4-5 per year (2022-2025), covering haematological disorders (haemophilia A/B;beta-thalassaemia; sickle cell disease), neuromuscular conditions (spinal muscular atrophy type 1; Duchenne musculardystrophy), metabolic diseases (lipoprotein lipase deficiency; ornithine transcarbamylase deficiency), and immunologicaldisorders (ADA-SCID; X-linked SCID). This systematic review evaluated 284 gene therapy studies in rare disorders(2,840 patient-treatment-outcome data points; Austrian rare disease gene therapy programme; haematology, neurology,and metabolic disease; 2015-2025) analysing clinical efficacy, durability, safety, and the vector platform-specificperformance. A Gene Therapy Clinical Index (GTCI) integrating efficacy magnitude, durability evidence, safety profile,and manufacturing scalability predicted sustained clinical benefit at 5 years with r = +0.84, identifying AAV-deliveredgene addition for haematological disorders as the highest-GTCI gene therapy approach with the most mature clinicalevidence base
2024-03-20 | Gene therapy for adenosine deaminase severe combined immune deficiency-An unexpected journey of four decades.
Severe combined immune deficiency due to adenosine deaminase deficiency (ADA SCID) is an inborn error of immunity with pan-lymphopenia, due to accumulated cytotoxic adenine metabolites. ADA SCID has been treated using gene therapy with a normal human ADA gene added to autologous hematopoietic stem cells (HSC) for over 30 years. Iterative improvements in vector design, HSC processing methods, and clinical HSC transplant procedures have led nearly all ADA SCID gene therapy patients to achieve consistently beneficial immune restoration with stable engraftment of ADA gene-corrected HSC over the duration of observation (as long as 20 years). One gene therapy for ADA SCID is approved by the European Medicines Agency (EMA) in the European Union (EU) and another is being advanced to licensure in the U.S. and U.K. Despite the clear-cut benefits and safety of this curative gene and cell therapy, it remains challenging to achieve sustained availability and access, especially for rare disorders like ADA SCID.
2023-06-14 | Updated Management Guidelines for Adenosine Deaminase Deficiency.
Inherited defects in the adenosine deaminase (ADA) gene typically cause severe combined immunodeficiency. In addition to infections, ADA-deficient patients can present with neurodevelopmental, behavioral, hearing, skeletal, lung, heart, skin, kidney, urogenital, and liver abnormalities. Some patients also suffer from autoimmunity and malignancies. In recent years, there have been remarkable advances in the management of ADA deficiency. Most ADA-deficient patients can be identified by newborn screening for severe combined immunodeficiency, which facilitates early diagnosis and treatment of asymptomatic infants. Most patients benefit from enzyme replacement therapy (ERT). Allogeneic hematopoietic cell transplantation from an HLA-matched sibling donor or HLA-matched family member donor with no conditioning is currently the preferable treatment. When matched sibling donor or matched family member donor is not available, autologous ADA gene therapy with nonmyeloablative conditioning and ERT withdrawal, which is reported in recent studies to result in 100% overall survival and 90% to 95% engraftment, should be pursued. If gene therapy is not immediately available, ERT can be continued for a few years, although its excessive cost might be prohibitive. The recent improved outcome of hematopoietic cell transplantation using HLA-mismatched family-related donors or HLA-matched unrelated donors, after reduced-intensity conditioning, suggests that such procedures might also be considered rather than continuing ERT for prolonged periods. Long-term follow-up will further assist in determining the optimal treatment approach for ADA-deficient patients.
2022-11-08 | Evaluation of clonal hematopoiesis in pediatric ADA-SCID gene therapy participants.
Autologous stem cell transplant with gene therapy (ASCT-GT) provides curative therapy while reducing pretransplant immune-suppressive conditioning and eliminating posttransplant immune suppression. Clonal hematopoiesis of indeterminate potential (CHIP)-associated mutations increase and telomere lengths (TLs) shorten with natural aging and DNA damaging processes. It is possible that, if CHIP is present before ASCT-GT or mutagenesis occurs after busulfan exposure, the hematopoietic stem cells carrying these somatic variants may survive the conditioning chemotherapy and have a selective reconstitution advantage, increasing the risk of hematologic malignancy and overall mortality. Seventy-four peripheral blood samples (ranging from baseline to 120 months after ASCT-GT) from 10 pediatric participants who underwent ASCT-GT for adenosine deaminase-deficient severe combined immune deficiency (ADA-SCID) after reduced-intensity conditioning with busulfan and 16 healthy controls were analyzed for TL and CHIP. One participant had a significant decrease in TL. There were no CHIP-associated mutations identified by the next-generation sequencing in any of the ADA-SCID participants. This suggests that further studies are needed to determine the utility of germline analyses in revealing the underlying genetic risk of malignancy in participants who undergo gene therapy. Although these results are promising, larger scale studies are needed to corroborate the effect of ASCT-GT on TL and CHIP. This trial was registered at www.clinicaltrials.gov as #NCT00794508.
proteins
2025-12-04 | Chlamydomonas Cellular Phenotypes Enable in vivo Validation of Computationally Designed Therapeutic ADA1 Variants
Poster presented at CellBio 2025 in Philadelphia, PA. December 2025Abstract:Adenosine deaminase (ADA) deficiency causes severe combined immunodeficiency, and current treatments include enzyme replacement therapy with immunogenic bovine proteins. To develop improved therapeutic variants, robust model systems are needed for testing rationally designed enzymes in vivo. We used Zoogle (zoogle.arcadiascience.com), a computational dataset that selects model organisms based on conserved protein characteristics rather than sequence similarity, to identify Chlamydomonas reinhardtii as an optimal system for studying human ADA1 function. This approach can identify effective models that traditional phylogenetic methods might overlook. We characterized Chlamydomonas ADA1 mutants and found clear phenotypic defects in motility and cellular metabolism, particularly altered starch accumulation under nutrient stress. We established quantitative phenotyping approaches, including high-throughput motility tracking, metabolic profiling via Raman spectroscopy, and biochemical staining to assess cellular function. These multi-modal readouts provided robust, reproducible measures of ADA1 activity in living cells. We're validating this system using wild-type human ADA1 and candidate variants designed through machine learning approaches to enhance stability and improve therapeutic properties. Initial results demonstrate that the algal system can detect functional differences in ADA1 variants, establishing a platform for screening computationally designed proteins. This approach enables systematic evaluation of engineered enzymes in a physiologically relevant cellular context. Our work establishes Chlamydomonas as an effective model for human metabolic enzymes and demonstrates the power of protein characteristic-based organism selection over traditional phylogenetic approaches. This validation platform enables rapid, cost-effective screening of designed therapeutic proteins before advancing to mammalian studies, potentially accelerating the development of next-generation enzyme replacement therapies for genetic diseases.
2023-06-28 | Rational engineering of an improved adenosine deaminase 2 enzyme for weaponizing T-cell therapies
Adenosine is a potent immunosuppressive metabolite that accumulates in the extracellular space within solid tumors and inhibits the antitumor function of native immune cells responses as well as chimeric antigen receptor (CAR) T cell therapies.Here, we show that engineered human cells can degrade extracellular adenosine through secretion of adenosine deaminase (ADA) enzymesa possible therapeutic enhancement for CAR T cells.We first determine that the high-activity ADA1 isoform is naturally intracellularly restricted and showed the addition of canonical or computationally predicted secretory peptides did not allow for improved secretion.We did, however, determine that the lower-activity ADA2 isoform is naturally secreted.Thus, we utilized phylogenetic-based structural comparisons to guide a mutational survey of ADA2 active site residues, which when coupled with a high throughput screen for enhanced ADA2-mediated extracellular adenosine rate, allowed isolation of the most catalytically efficient ADA2 variant reported to date.When expressed by human cells, this variant exhibits 30x higher extracellular adenosine degradation activity than the wildtype enzyme.Finally, we demonstrate that Jurkat and CAR T cells engineered to express this secreted, high-activity ADA2 variant can degrade significant amounts of extracellular adenosine in vitro.J o u r n a l P r e -p r o o f Highlights • Adenosine deaminase secretion could allow immune cells to resist immunosuppression • Adenosine deaminase 2 (ADA2) can be secreted from human cells but ADA1 cannot • ADA2 has much lower catalytic activity than ADA1 • Utilized directed evolution to greatly improve ADA2's catalytic activity • Jurkat and CAR T cells can secrete an improved ADA2 enzyme to degrade adenosine
2018-11-01 | Narrative review of severe combined immunodeficiency—a purine metabolism disorder
Severe combined immunodeficiency (SCID) is a primary immune deficiency that is a pediatric emergency. Left untreated, patients will die prior to 2 years of age from overwhelming infection. There are many known causes of SCID, but this review focuses on adenosine deaminase (ADA) deficiency. ADA is a ubiquitous “housekeeping” enzyme, and its deficiency leads to buildup of toxic metabolites, which preferentially affects lymphocytes but also causes non-immune manifestations of disease. While previously diagnosed based on recurrent, severe, or unusual infection, SCID is now being diagnosed during its initial asymptomatic period thanks to recent implementation of T cell receptor excision circle (TREC) newborn screening, thus greatly improving survival of patients as treatment can occur before the onset of infection. To date, TREC screening has shown 100% sensitivity for SCID but also has brought to light other causes of T cell lymphopenia that were previously lesser known. ADA-deficient SCID can be treated through enzyme replacement therapy (ERT), hematopoietic stem cell transplantation (HSCT), or gene therapy, and advances continue to be made every day that improve cost-effectiveness and efficacy of these therapies and make them more widely available to patients.
2007-07-07 | A 9‐yr evaluation of carrier erythrocyte encapsulated adenosine deaminase (ADA) therapy in a patient with adult‐type ADA deficiency
Abstract Adenosine deaminase (ADA) deficiency is an inherited disorder which leads to elevated cellular levels of deoxyadenosine triphosphate (dATP) and systemic accumulation of its precursor, 2‐deoxyadenosine. These metabolites impair lymphocyte function, and inactivate S‐adenosylhomocysteine hydrolase (SAHH) respectively, leading to severe immunodeficiency. Enzyme replacement therapy with polyethylene glycol‐conjugated ADA is available, but its efficacy is reduced by anti‐ADA neutralising antibody formation. We report here carrier erythrocyte encapsulated native ADA therapy in an adult‐type ADA deficient patient. Encapsulated enzyme is protected from antigenic responses and therapeutic activities are sustained. ADA‐loaded autologous carrier erythrocytes were prepared using a hypo‐osmotic dialysis procedure. Over a 9‐yr period 225 treatment cycles were administered at 2–3 weekly intervals. Therapeutic efficacy was determined by monitoring immunological and metabolic parameters. After 9 yr of therapy, erythrocyte dATP concentration ranged between 24 and 44 μmol/L (diagnosis, 234) and SAHH activity between 1.69 and 2.29 nmol/h/mg haemoglobin (diagnosis, 0.34). Erythrocyte ADA activities were above the reference range of 40–100 nmol/h/mg haemoglobin (0 at diagnosis). Initial increases in absolute lymphocyte counts were not sustained; however, despite subnormal circulating CD20 + cell numbers, serum immunoglobulin levels were normal. The patient tolerated the treatment well. The frequency of respiratory problems was reduced and the decline in the forced expiratory volume in 1 s and vital capacity reduced compared with the 4 yr preceding carrier erythrocyte therapy. Carrier erythrocyte‐ADA therapy in an adult patient with ADA deficiency was shown to be metabolically and clinically effective.
2002-04-26 | Immobilization of Adenosine Deaminase onto Agarose and Casein
In the present study adenosine deaminase (ADA) was immobilized onto two different polymeric materials, agarose and casein. The factors affecting the amount of enzyme attachment onto the polymeric supports such as incubation time were investigated. The maximum amount of enzyme immobilized onto different polymeric supports occurred at incubation pH value 7.5 and ADA concentration 42 units/g and the incubation time needed for the maximum amount of enzyme attachment to the polymeric supports was found to be 8 h. Some phsicochemical properties of the free and immobilized ADA such as operational stability, optimum temperature and thermal stability, pH optimum and stability, storage stability, and the effect of gamma-radiation were studied. The operational stability of the free and immobilized enzyme showed that the enzyme immobilized by a cross-linking technique using gultaric dialdehyde showed poor durability and the relative activity decreased sharply due to the leakage after repeated washing, while the enzymes immobilized by covalent bonds to the carriers showed a slight decrease in most cases in the relative activity (around 20%) after being used 10 times. Storage for 4-6 months, showed that the free enzyme lost its activity, while the immobilized enzyme showed the opposite behavior. Subjecting the immobilized enzyme to a dose of gamma radiation of 0.5-10 Mrad showed complete loss in the activity of the free enzyme at a dose of 5 Mrad, while the immobilized enzymes showed relatively high resistance to gamma radiation up to a dose of 5 Mrad.
other
2025-11-21 | Dupilumab for atopic manifestations in pediatric patients with inborn errors of immunity: efficacy and safety in a genetically diverse cohort
Background Inborn Errors of Immunity (IEI) are monogenic disorders that predispose patients to infections, autoimmunity, atopy, and malignancies. Severe Th2-driven atopic dermatitis and asthma are common in several IEIs, including DOCK8 deficiency, STAT3 loss-of-function, and Wiskott–Aldrich syndrome, often refractory to conventional therapies. Dupilumab, a monoclonal antibody targeting IL-4Rα, has shown promise in managing recalcitrant atopic dermatitis and asthma, but data in immunocompromised pediatric populations remain limited. Methods We conducted a single-center, retrospective observational cohort study with prospective follow-up of ten pediatric patients with genetically confirmed IEI and atopic manifestations. Patients received subcutaneous dupilumab (300 mg every 4 weeks for atopic dermatitis; every 2 weeks for severe asthma). Outcomes were assessed using the Eczema Area and Severity Index (EASI), Dermatology Life Quality Index (DLQI), Childhood Asthma Control Test (C-ACT), eosinophil counts, and infection frequency across four time points (baseline, 6 months, 12 months, >18 months). Results The cohort included ten patients (6 males, 4 females) with mutations in DOCK8 (n=5), CARD11 (n=2), STAT3 LOF (n=1), ADA (n=1), and PEPD (n=1). Of ten patients, nine received dupilumab for atopic dermatitis. Baseline EASI and DLQI scores were 34.33 and 25.0, respectively. Following dupilumab therapy, mean EASI decreased to 2.67 (p<0.001) and DLQI improved to 2.67 (p<0.001), with sustained response observed over 18 months. Peripheral eosinophil counts declined from 2.0×10 9 /L to 0.45×10 9 /L (p<0.001). One patient with severe asthma achieved C-ACT improvement from 10 to 26 with no subsequent exacerbations. Treatment was well-tolerated, with only mild conjunctivitis or transient hypereosinophilia reported. Notably, skin infections resolved, and no systemic or opportunistic infections were observed. Conclusion Dupilumab is a safe and highly effective therapeutic option for pediatric patients with IEI-associated atopic manifestations, improving clinical outcomes, quality of life, and infection profile while preserving immune function. These findings support broader application of dupilumab in patients with IEI and warrant further investigation in larger, multicenter studies.
2021-05-27 | Emapalumab treatment in an ADA-SCID patient with refractory hemophagocytic lymphohistiocytosis-related graft failure and disseminated bacillus Calmette-Guérin infection.
Emapalumab, a fully human anti-IFNγ monoclonal antibody, has been approved in the US as second-line treatment of primary hemophagocytic lymphohistiocytosis (HLH) patients and has shown promise in patients with graft failure (GF) requiring a second allogeneic hematopoietic stem cell transplantation (HSCT). The blockade of IFNγ activity may increase the risk of severe infections, including fatal mycobacteriosis. We report a case of secondary HLH-related GF in the context of HLA-haploidentical HSCT successfully treated with emapalumab in the presence of concomitant life-threatening infections, including disseminated tuberculosis (TB). A 4 years old girl with Adenosine Deaminase-Severe Combined Immunodeficiency complicated by disseminated TB came to our attention for ex-vivo hematopoietic stem cell-gene therapy. After engraftment failure of gene corrected cells, she received two HLA-haploidentical T-cell depleted HSCT from the father, both failed due to GF related to concomitant multiple infections and secondary HLH. Emapalumab administration allowed to control HLH, as well as to prevent GF after a third haplo-HSCT from the mother. Remarkably, all infections improved with antimicrobial medications and disseminated TB did not show any reactivation. This seminal case supports emapalumab use for treatment of secondary HLH and prevention of GF in patients undergoing haplo-HSCT even in the presence of multiple infections, including TB.
small molecules
2025-07-01 | Synthetic approaches and biological functions of 2 deoxyadenosine: A review of nucleoside chemistry and cellular dynamics
2′ Deoxyadenosine (dAdo) resides at the critical junction of de novo and salvage deoxyribonucleotide synthesis while salvage phosphorylation of dAdo replenishes the dATP-pool, the de novo pathway via ribonucleotide reductase (RNR) generates dNTPs from ribonucleotides. Disruption of this balance as typified in adenosine deaminase (ADA) deficiency causes intracellular dAdo and dATP accumulation, potent RNR inhibition, dNTP‐pool disruption and replication stress. Concurrently, synthetic modification of the dAdo scaffold has driven the development of analogues that exploit nucleoside transporters, resist deaminative inactivation and selectively accumulate in target cells to modulate DNA repair, immune signalling and mitochondrial DNA maintenance. This review presents a unified account of dAdo’s structural and molecular properties, its role in dNTP homeostasis and cellular dynamics, the pathological consequences of salvage/de novo dysregulation, and the latest synthetic and medicinal chemistry strategies built on the dAdo framework.
2025-06-27 | Adenosine and Adenosine Deaminase Contrary Manifestations in Immunity.
Adenosine (Ado) is an important purine that regulates numerous physiological functions. Adenosine deaminase (ADA) catalyses the irreversible deamination of Ado and its derivatives. Ado and ADA are the essential players in the immune system, but their roles often are opposite, mutually exclusive and competitive. This work presents several critical immune system situations demonstrating the conflicts between the functions of Ado and ADA. Ado suppresses immunity and inflammation by inhibiting lymphocyte proliferation. ADA supports the development of the immune system by metabolising Ado. In infectious and inflamed diseases, the increased ADA levels in tissue exudates decrease Ado concentration, aggravating inflammation. ADA inhibition is required to protect Ado and mitigate inflammation. In hereditary ADA deficiency, cytotoxic metabolites of Ado accumulate in lymphocytes and suppress immunity. ADA deficiency became the second cause of severe combined immunodeficiency (SCID). Enzyme replacement therapy using PEGylated ADA and ADA gene therapy are recognised in ADA-SCID treatment. The human immunodeficiency virus (HIV) hyperactivates host immune cells, resulting in super-inflammation and acquired immunodeficiency syndrome (AIDS). Cytotoxic derivatives of Ado suppress HIV-1 growth, whereas ADA inactivates cytotoxic nucleosides. ADA inhibition is required to prolong the elimination time and reduce the effective doses of anti-AIDS drugs. Ado levels elevate in the tumour microenvironment, promote immunity suppression and condition tumour cell evasion of immune surveillance. ADA neutralises Ado and restores immunity. Furthermore, ADA can simultaneously bind to the CD26 protein on lymphocytes and the A2AR receptors on antigen-presenting dendritic cells. Created CD26-ADA-A2AR complex bridges T and dendritic cells, stimulating T lymphocyte function.
2023-08-11 | Computational 3D structure prediction followed by molecular docking to reveal the novel drug targets against ADA
Adenosine deaminase (ADA) is a functional enzyme that transforms deoxyadenosine and adenosine into deoxyinosine and inosine respectively. ADA deficiency causes toxic purine degradation byproducts to build up in the body, which has a particularly negative impact on lymphocytes and results in adenosine deaminase-deficient severe combined immunodeficiency. Different in silico techniques including threading, ab initio and homology modeling for 3D structure prediction were applied for the prediction of ADA structures. Following the three-dimensional structure prediction analyses, an extensive computational assessment of all predicted structures for reliability was performed. The overall quality factor of the predicted ADA structures was observed 62.45% in the predicted 3D models. A Ramachandran plot was created, and 94.80% of the residues were found in the allowed and favored regions of the protein structure plot. The molecular docking analyses were performed in order to identify the potential therapeutic medication targets against ADA. The virtually examined molecules through a virtually high throughput screening may have the ability the regulation the ADA activity. The least binding energy was calculated through the molecular docking analyses and the energy values were observed -8.7 Kcal/mol. The binding residues (Lys-367, Glu-424, Asp-422, Phe-381, Ile-377, Ser-430 and Glu-374) were conserved in all the interactional analyses of the docked complexes. Finding the effective binding domain in a protein three-dimensional structure is crucial for understanding of its structural makeup and determining its functions.
2021-04-27 | Adenosine A2B receptor: A pathogenic factor and a therapeutic target for sensorineural hearing loss.
Over 466 million people worldwide are diagnosed with hearing loss (HL). About 90% of HL cases are sensorineural HL (SNHL) with treatments limited to hearing aids and cochlear implants with no FDA-approved drugs. Intriguingly, ADA-deficient patients have been reported to have bilateral SNHL, however, its underlying cellular and molecular basis remain unknown. We report that Ada-/- mice, phenocopying ADA-deficient humans, displayed SNHL. Ada-/- mice cochlea with elevated adenosine caused substantial nerve fiber demyelination and mild hair cell loss. ADA enzyme therapy in these mice normalized cochlear adenosine levels, attenuated SNHL, and prevented demyelination. Additionally, ADA enzyme therapy rescued SNHL by restoring nerve fiber structure in Ada-/- mice post two-week drug withdrawal. Moreover, elevated cochlear adenosine in untreated mice was associated with enhanced Adora2b gene expression. Preclinically, ADORA2B-specific antagonist treatment in Ada-/- mice significantly improved HL, nerve fiber density, and myelin compaction. We also provided genetic evidence that ADORA2B is detrimental for age-related SNHL by impairing cochlear myelination in WT aged mice. Overall, understanding purinergic molecular signaling in SNHL in Ada-/- mice allows us to further discover that ADORA2B is also a pathogenic factor underlying aged-related SNHL by impairing cochlear myelination and lowering cochlear adenosine levels or blocking ADORA2B signaling are effective therapies for SNHL.
2020-12-30 | In vitro adenosine deaminase inhibitory activity of some selected plant extracts and chemical compounds
Background and Aims: Adenosine deaminase (EC 3.5.4.4, ADA) is distributed in all human tissues. It catalyses the deamination of adenosine (deoxyadenosine) to inosine (deoxyinosine) via removal of an amino group. The determination of ADAinhibition is of extreme significance in the field of fundamental research and clinical diagnosis. In our study, the effects of various plant extracts and chemicals on ADA activity were investigated. Methods: Adenosine deaminase activity was determined spectrophotometrically at 625 nm. Results: The inhibitory activities of the extracts and chemical compounds increased in a dose-dependent manner. Among the plant extracts used, lemon extract was observed to exhibit the highest ADA inhibition activity with an IC50 value of 0.05 ± 0.001 mg/mL, while quercetin had the highest ADA inhibition (IC50 value of 0.004±0.0005 mg/mL) among the chemical compounds. All plant extracts and chemical compounds showed ADA inhibition activities. Conclusion: The obtained results indicate that plant extracts and some chemical compounds examined in this study can be a potential source of novel ADA-inhibitors for therapeutics.
cell therapies
2025-11-25 | Outcomes following matched sibling donor transplantation for severe combined immunodeficiency: a report from the PIDTC
ABSTRACT: The Primary Immune Deficiency Treatment Consortium performed a retrospective analysis of 133 patients with severe combined immunodeficiency (SCID) receiving matched sibling donor (MSD) hematopoietic cell transplantation (HCT) between 1980 and 2023 at 30 North American institutions. In this largest cohort of MSD outcomes in patients with SCID to date, we examined the impact of conditioning regimen and graft-versus-host disease (GVHD) prophylaxis on survival and immune recovery. Outcomes after MSD HCT for SCID were excellent. Patients without an active infection or failure to thrive (FTT) at the time of HCT had 5-year overall survival superior to those with infection or FTT. Acute and chronic GVHD outcomes were independent of GVHD prophylaxis, conditioning regimen, SCID type, or presence of maternal engraftment. Patients without active infection at the time of HCT had superior chronic GVHD-free event-free survival vs those with infection. T-cell reconstitution at 6 months was less likely achieved with use of GVHD prophylaxis or serotherapy, and in patients with leaky SCID or Omenn syndrome. At 6 months, 1 year, and 2-5 years, T-cell reconstitution was less likely with ADA, DCLRE1C, or RAG genotype. B-cell reconstitution at 1 year and 2-5 years was negatively affected by development of grade 2 to 4 or 3 to 4 acute GVHD. Conditioning did not affect T- or B-cell reconstitution. Our data suggest omitting conditioning and GVHD prophylaxis for patients with typical SCID did not negatively affect 5-year outcomes after MSD HCT, but the data are insufficient to recommend this approach for best long-term outcomes. This trial was registered at www.clinicaltrials.gov as #NCT01186913 and #NCT01346150.
2022-06-07 | Outcomes following treatment for ADA-deficient severe combined immunodeficiency: a report from the PIDTC
Abstract Adenosine deaminase (ADA) deficiency causes ∼13% of cases of severe combined immune deficiency (SCID). Treatments include enzyme replacement therapy (ERT), hematopoietic cell transplant (HCT), and gene therapy (GT). We evaluated 131 patients with ADA-SCID diagnosed between 1982 and 2017 who were enrolled in the Primary Immune Deficiency Treatment Consortium SCID studies. Baseline clinical, immunologic, genetic characteristics, and treatment outcomes were analyzed. First definitive cellular therapy (FDCT) included 56 receiving HCT without preceding ERT (HCT); 31 HCT preceded by ERT (ERT-HCT); and 33 GT preceded by ERT (ERT-GT). Five-year event-free survival (EFS, alive, no need for further ERT or cellular therapy) was 49.5% (HCT), 73% (ERT-HCT), and 75.3% (ERT-GT; P < .01). Overall survival (OS) at 5 years after FDCT was 72.5% (HCT), 79.6% (ERT-HCT), and 100% (ERT-GT; P = .01). Five-year OS was superior for patients undergoing HCT at <3.5 months of age (91.6% vs 68% if ≥3.5 months, P = .02). Active infection at the time of HCT (regardless of ERT) decreased 5-year EFS (33.1% vs 68.2%, P < .01) and OS (64.7% vs 82.3%, P = .02). Five-year EFS (90.5%) and OS (100%) were best for matched sibling and matched family donors (MSD/MFD). For patients treated after the year 2000 and without active infection at the time of FDCT, no difference in 5-year EFS or OS was found between HCT using a variety of transplant approaches and ERT-GT. This suggests alternative donor HCT may be considered when MSD/MFD HCT and GT are not available, particularly when newborn screening identifies patients with ADA-SCID soon after birth and before the onset of infections. This trial was registered at www.clinicaltrials.gov as #NCT01186913 and #NCT01346150.
2022-03-15 | Hematopoietic Cell Transplantation for Adenosine Deaminase Severe Combined Immunodeficiency—Improved Outcomes in the Modern Era
Current treatment for adenosine deaminase (ADA)-deficient severe combined immunodeficiency (SCID) includes enzyme replacement therapy (ERT), allogeneic hematopoietic stem cell transplant (HSCT), or ex vivo corrected autologous hematopoietic stem cell gene therapy. Historic data show HSCT survival is superior using unconditioned matched sibling and family compared to matched unrelated and haploidentical donors. Recent improvement in HSCT outcomes prompted us to retrospectively examine HSCT survival and long-term graft function in ADA-SCID transplanted at our center. Thirty-three ADA-deficient patients received HSCT between 1989 and 2020, with follow-up data to January 2021. Chemotherapy conditioning regimens were defined as myeloablative (MAC-busulfan/cyclophosphamide), reduced-toxicity myeloablative (RT-MAC-treosulfan-based, since 2007), or no conditioning. Serotherapy used included alemtuzumab (with or without other conditioning agents) or antithymocyte globulin (ATG). ERT was introduced routinely in 2010 until commencement of conditioning. Median age at HSCT was 3.2 (0.8-99.8) months. Twenty-one (63.6%) received stem cells from unrelated or haploidentical donors. Seventeen (51.5%) received chemotherapy conditioning and 16 (48.5%) received alemtuzumab. Median follow-up was 7.5 (0.8-25.0) years. Overall survival (OS) and event-free survival (EFS) at 8 years were 90.9% (95% CI: 79.7-100.0%) and 79% (55-91%), respectively. OS after 2007 (n = 21) was 100% vs 75% before 2007 (n = 12) (p = 0.02). Three (9.1%) died after HSCT: two from multiorgan failure and one from unexplained encephalopathy. There were no deaths after 2007, among those who received ERT and treosulfan-based conditioning pre-HSCT. Ten (30.3%) developed acute GvDH (3 grade II, 2 grade III); no chronic GvHD was observed. In the modern era, conditioned HSCT with MUD has a favorable outcome for ADA-deficient patients.
2022-01-31 | Successful engraftment of haploidentical stem cell transplant with post-transplantation cyclophosphamide in a patient with adenosine deaminase deficiency.
SCID are characterized by an imbalance in cellular and humoral immunity. Enzyme ADA deficiency represents from 10% to 15% of the SCID. This generates diminished maturation of the cell precursors. Treatments include enzyme replacement therapy, allogenic, or autologous HSCT with gene therapy, with HSCT being of choice when an identical HLA donor exists. Male patient, without relevant family antecedents or consanguinity. The patient had multiple infections during the first months of life, evidencing low immunoglobulin levels, with absence of T and B lymphocytes, and natural killer cells. Severe combined immunodeficiencies are considered due to ADA deficiency; management was begun and is derived to our hospital. Admission at 8 months of life, with chronic malnutrition and psychomotor retardation. The HLA studies were conducted without finding an identical donor, taken to HSCT with haploidentical donor. Conditioning regimen with cyclophosphamide, fludarabine, melphalan, and thymoglobulin. This patient received prophylaxis for graft-versus-host disease with cyclophosphamide, cyclosporine, and methotrexate. A 22 months post-transplant, the patient was without immunosuppressants or immunoglobulin, without evidence of graft-versus-host disease or new infections. The ADA deficiency is an infrequent pathology that can be potentially fatal if adequate treatment is not started. Haploidentical HSCT, using post-transplantation cyclophosphamide, emerges as a viable option with which good results can be achieved and improve the quality of life in patients with no other therapeutic alternatives.
2021-10-28 | Hematopoietic cell transplantation in severe combined immunodeficiency: The SCETIDE 2006-2014 European cohort
Hematopoietic stem cell transplantation (HSCT) represents a curative treatment for patients with severe combined immunodeficiency (SCID), a group of monogenic immune disorders with an otherwise fatal outcome.We performed a comprehensive multicenter analysis of genotype-specific HSCT outcome, including detailed analysis of immune reconstitution (IR) and the predictive value for clinical outcome.HSCT outcome was studied in 338 patients with genetically confirmed SCID who underwent transplantation in 2006-2014 and who were registered in the SCETIDE registry. In a representative subgroup of 152 patients, data on IR and long-term clinical outcome were analyzed.Two-year OS was similar with matched family and unrelated donors and better than mismatched donor HSCT (P < .001). The 2-year event-free survival (EFS) was similar in matched and mismatched unrelated donor and less favorable in mismatched related donor (MMRD) HSCT (P < .001). Genetic subgroups did not differ in 2-year OS (P = .1) and EFS (P = .073). In multivariate analysis, pretransplantation infections and use of MMRDs were associated with less favorable OS and EFS. With a median follow-up of 6.2 years (range, 2.0-11.8 years), 73 of 152 patients in the IR cohort were alive and well without Ig dependency. IL-2 receptor gamma chain/Janus kinase 3/IL-7 receptor-deficient SCID, myeloablative conditioning, matched donor HSCT, and naive CD4 T lymphocytes >0.5 × 10e3/μL at +1 year were identified as independent predictors of favorable clinical and immunologic outcome.Recent advances in HSCT in SCID patients have resulted in improved OS and EFS in all genotypes and donor types. To achieve a favorable long-term outcome, treatment strategies should aim for optimal naive CD4 T lymphocyte regeneration.
gene therapies
2025-06-04 | Quantifying the mutational landscape of retroviral and lentiviral vectors in gene therapy patients.
Adenosine deaminase severe combined immunodeficiency (ADA-SCID) is a monogenic disorder caused by mutations in the ADA gene. Gene therapy using γ-retroviral and lentiviral vector gene addition approaches have shown curative results. We sequenced the ADA transgene in transduced CD3+ T cells, and in peripheral blood cells from patients treated with autologous CD34+ cells transduced with either a γ-retroviral or lentiviral ADA gene vector to assess transgene mutational profiles. In both CD3+ T cells and ADA-SCID patients' cells treated with the lentiviral vector, we observed significantly higher occurrences of guanine (G)-to-adenosine (A) base substitutions than with the γ-retroviral vector. We hypothesized that this G-to-A mutational signature was due to the APOBEC3 cytosine deaminase protein family. By knocking out APOBEC3 genes in HEK239T packaging cells, APOBEC3-mediated mutagenesis decreased by 91.2% along the transgene in CD34+ transduced cells in comparison to CD34+ cells transduced with lentiviral supernatant packaged in parental HEK293T cells.
2025-04-15 | Gene Therapy in Rare Disorders
Gene therapy -- the delivery of therapeutic nucleic acids (DNA; RNA; oligonucleotides) to correct, silence, or replacedisease-causing genetic alterations -- has achieved its most transformative clinical results in rare monogenic disorderswhere a single gene defect causes a well-defined, severe, and progressive disease amenable to genetic correction. Thepast decade has seen 18 gene therapy marketing authorisations in the EU (2012-2025), with the pace accelerating from1-2 approvals per year (2015-2018) to 4-5 per year (2022-2025), covering haematological disorders (haemophilia A/B;beta-thalassaemia; sickle cell disease), neuromuscular conditions (spinal muscular atrophy type 1; Duchenne musculardystrophy), metabolic diseases (lipoprotein lipase deficiency; ornithine transcarbamylase deficiency), and immunologicaldisorders (ADA-SCID; X-linked SCID). This systematic review evaluated 284 gene therapy studies in rare disorders(2,840 patient-treatment-outcome data points; Austrian rare disease gene therapy programme; haematology, neurology,and metabolic disease; 2015-2025) analysing clinical efficacy, durability, safety, and the vector platform-specificperformance. A Gene Therapy Clinical Index (GTCI) integrating efficacy magnitude, durability evidence, safety profile,and manufacturing scalability predicted sustained clinical benefit at 5 years with r = +0.84, identifying AAV-deliveredgene addition for haematological disorders as the highest-GTCI gene therapy approach with the most mature clinicalevidence base
2024-03-20 | Gene therapy for adenosine deaminase severe combined immune deficiency-An unexpected journey of four decades.
Severe combined immune deficiency due to adenosine deaminase deficiency (ADA SCID) is an inborn error of immunity with pan-lymphopenia, due to accumulated cytotoxic adenine metabolites. ADA SCID has been treated using gene therapy with a normal human ADA gene added to autologous hematopoietic stem cells (HSC) for over 30 years. Iterative improvements in vector design, HSC processing methods, and clinical HSC transplant procedures have led nearly all ADA SCID gene therapy patients to achieve consistently beneficial immune restoration with stable engraftment of ADA gene-corrected HSC over the duration of observation (as long as 20 years). One gene therapy for ADA SCID is approved by the European Medicines Agency (EMA) in the European Union (EU) and another is being advanced to licensure in the U.S. and U.K. Despite the clear-cut benefits and safety of this curative gene and cell therapy, it remains challenging to achieve sustained availability and access, especially for rare disorders like ADA SCID.
2023-06-14 | Updated Management Guidelines for Adenosine Deaminase Deficiency.
Inherited defects in the adenosine deaminase (ADA) gene typically cause severe combined immunodeficiency. In addition to infections, ADA-deficient patients can present with neurodevelopmental, behavioral, hearing, skeletal, lung, heart, skin, kidney, urogenital, and liver abnormalities. Some patients also suffer from autoimmunity and malignancies. In recent years, there have been remarkable advances in the management of ADA deficiency. Most ADA-deficient patients can be identified by newborn screening for severe combined immunodeficiency, which facilitates early diagnosis and treatment of asymptomatic infants. Most patients benefit from enzyme replacement therapy (ERT). Allogeneic hematopoietic cell transplantation from an HLA-matched sibling donor or HLA-matched family member donor with no conditioning is currently the preferable treatment. When matched sibling donor or matched family member donor is not available, autologous ADA gene therapy with nonmyeloablative conditioning and ERT withdrawal, which is reported in recent studies to result in 100% overall survival and 90% to 95% engraftment, should be pursued. If gene therapy is not immediately available, ERT can be continued for a few years, although its excessive cost might be prohibitive. The recent improved outcome of hematopoietic cell transplantation using HLA-mismatched family-related donors or HLA-matched unrelated donors, after reduced-intensity conditioning, suggests that such procedures might also be considered rather than continuing ERT for prolonged periods. Long-term follow-up will further assist in determining the optimal treatment approach for ADA-deficient patients.
2022-11-08 | Evaluation of clonal hematopoiesis in pediatric ADA-SCID gene therapy participants.
Autologous stem cell transplant with gene therapy (ASCT-GT) provides curative therapy while reducing pretransplant immune-suppressive conditioning and eliminating posttransplant immune suppression. Clonal hematopoiesis of indeterminate potential (CHIP)-associated mutations increase and telomere lengths (TLs) shorten with natural aging and DNA damaging processes. It is possible that, if CHIP is present before ASCT-GT or mutagenesis occurs after busulfan exposure, the hematopoietic stem cells carrying these somatic variants may survive the conditioning chemotherapy and have a selective reconstitution advantage, increasing the risk of hematologic malignancy and overall mortality. Seventy-four peripheral blood samples (ranging from baseline to 120 months after ASCT-GT) from 10 pediatric participants who underwent ASCT-GT for adenosine deaminase-deficient severe combined immune deficiency (ADA-SCID) after reduced-intensity conditioning with busulfan and 16 healthy controls were analyzed for TL and CHIP. One participant had a significant decrease in TL. There were no CHIP-associated mutations identified by the next-generation sequencing in any of the ADA-SCID participants. This suggests that further studies are needed to determine the utility of germline analyses in revealing the underlying genetic risk of malignancy in participants who undergo gene therapy. Although these results are promising, larger scale studies are needed to corroborate the effect of ASCT-GT on TL and CHIP. This trial was registered at www.clinicaltrials.gov as #NCT00794508.
proteins
2025-12-04 | Chlamydomonas Cellular Phenotypes Enable in vivo Validation of Computationally Designed Therapeutic ADA1 Variants
Poster presented at CellBio 2025 in Philadelphia, PA. December 2025Abstract:Adenosine deaminase (ADA) deficiency causes severe combined immunodeficiency, and current treatments include enzyme replacement therapy with immunogenic bovine proteins. To develop improved therapeutic variants, robust model systems are needed for testing rationally designed enzymes in vivo. We used Zoogle (zoogle.arcadiascience.com), a computational dataset that selects model organisms based on conserved protein characteristics rather than sequence similarity, to identify Chlamydomonas reinhardtii as an optimal system for studying human ADA1 function. This approach can identify effective models that traditional phylogenetic methods might overlook. We characterized Chlamydomonas ADA1 mutants and found clear phenotypic defects in motility and cellular metabolism, particularly altered starch accumulation under nutrient stress. We established quantitative phenotyping approaches, including high-throughput motility tracking, metabolic profiling via Raman spectroscopy, and biochemical staining to assess cellular function. These multi-modal readouts provided robust, reproducible measures of ADA1 activity in living cells. We're validating this system using wild-type human ADA1 and candidate variants designed through machine learning approaches to enhance stability and improve therapeutic properties. Initial results demonstrate that the algal system can detect functional differences in ADA1 variants, establishing a platform for screening computationally designed proteins. This approach enables systematic evaluation of engineered enzymes in a physiologically relevant cellular context. Our work establishes Chlamydomonas as an effective model for human metabolic enzymes and demonstrates the power of protein characteristic-based organism selection over traditional phylogenetic approaches. This validation platform enables rapid, cost-effective screening of designed therapeutic proteins before advancing to mammalian studies, potentially accelerating the development of next-generation enzyme replacement therapies for genetic diseases.
2023-06-28 | Rational engineering of an improved adenosine deaminase 2 enzyme for weaponizing T-cell therapies
Adenosine is a potent immunosuppressive metabolite that accumulates in the extracellular space within solid tumors and inhibits the antitumor function of native immune cells responses as well as chimeric antigen receptor (CAR) T cell therapies.Here, we show that engineered human cells can degrade extracellular adenosine through secretion of adenosine deaminase (ADA) enzymesa possible therapeutic enhancement for CAR T cells.We first determine that the high-activity ADA1 isoform is naturally intracellularly restricted and showed the addition of canonical or computationally predicted secretory peptides did not allow for improved secretion.We did, however, determine that the lower-activity ADA2 isoform is naturally secreted.Thus, we utilized phylogenetic-based structural comparisons to guide a mutational survey of ADA2 active site residues, which when coupled with a high throughput screen for enhanced ADA2-mediated extracellular adenosine rate, allowed isolation of the most catalytically efficient ADA2 variant reported to date.When expressed by human cells, this variant exhibits 30x higher extracellular adenosine degradation activity than the wildtype enzyme.Finally, we demonstrate that Jurkat and CAR T cells engineered to express this secreted, high-activity ADA2 variant can degrade significant amounts of extracellular adenosine in vitro.J o u r n a l P r e -p r o o f Highlights • Adenosine deaminase secretion could allow immune cells to resist immunosuppression • Adenosine deaminase 2 (ADA2) can be secreted from human cells but ADA1 cannot • ADA2 has much lower catalytic activity than ADA1 • Utilized directed evolution to greatly improve ADA2's catalytic activity • Jurkat and CAR T cells can secrete an improved ADA2 enzyme to degrade adenosine
2018-11-01 | Narrative review of severe combined immunodeficiency—a purine metabolism disorder
Severe combined immunodeficiency (SCID) is a primary immune deficiency that is a pediatric emergency. Left untreated, patients will die prior to 2 years of age from overwhelming infection. There are many known causes of SCID, but this review focuses on adenosine deaminase (ADA) deficiency. ADA is a ubiquitous “housekeeping” enzyme, and its deficiency leads to buildup of toxic metabolites, which preferentially affects lymphocytes but also causes non-immune manifestations of disease. While previously diagnosed based on recurrent, severe, or unusual infection, SCID is now being diagnosed during its initial asymptomatic period thanks to recent implementation of T cell receptor excision circle (TREC) newborn screening, thus greatly improving survival of patients as treatment can occur before the onset of infection. To date, TREC screening has shown 100% sensitivity for SCID but also has brought to light other causes of T cell lymphopenia that were previously lesser known. ADA-deficient SCID can be treated through enzyme replacement therapy (ERT), hematopoietic stem cell transplantation (HSCT), or gene therapy, and advances continue to be made every day that improve cost-effectiveness and efficacy of these therapies and make them more widely available to patients.
2007-07-07 | A 9‐yr evaluation of carrier erythrocyte encapsulated adenosine deaminase (ADA) therapy in a patient with adult‐type ADA deficiency
Abstract Adenosine deaminase (ADA) deficiency is an inherited disorder which leads to elevated cellular levels of deoxyadenosine triphosphate (dATP) and systemic accumulation of its precursor, 2‐deoxyadenosine. These metabolites impair lymphocyte function, and inactivate S‐adenosylhomocysteine hydrolase (SAHH) respectively, leading to severe immunodeficiency. Enzyme replacement therapy with polyethylene glycol‐conjugated ADA is available, but its efficacy is reduced by anti‐ADA neutralising antibody formation. We report here carrier erythrocyte encapsulated native ADA therapy in an adult‐type ADA deficient patient. Encapsulated enzyme is protected from antigenic responses and therapeutic activities are sustained. ADA‐loaded autologous carrier erythrocytes were prepared using a hypo‐osmotic dialysis procedure. Over a 9‐yr period 225 treatment cycles were administered at 2–3 weekly intervals. Therapeutic efficacy was determined by monitoring immunological and metabolic parameters. After 9 yr of therapy, erythrocyte dATP concentration ranged between 24 and 44 μmol/L (diagnosis, 234) and SAHH activity between 1.69 and 2.29 nmol/h/mg haemoglobin (diagnosis, 0.34). Erythrocyte ADA activities were above the reference range of 40–100 nmol/h/mg haemoglobin (0 at diagnosis). Initial increases in absolute lymphocyte counts were not sustained; however, despite subnormal circulating CD20 + cell numbers, serum immunoglobulin levels were normal. The patient tolerated the treatment well. The frequency of respiratory problems was reduced and the decline in the forced expiratory volume in 1 s and vital capacity reduced compared with the 4 yr preceding carrier erythrocyte therapy. Carrier erythrocyte‐ADA therapy in an adult patient with ADA deficiency was shown to be metabolically and clinically effective.
2002-04-26 | Immobilization of Adenosine Deaminase onto Agarose and Casein
In the present study adenosine deaminase (ADA) was immobilized onto two different polymeric materials, agarose and casein. The factors affecting the amount of enzyme attachment onto the polymeric supports such as incubation time were investigated. The maximum amount of enzyme immobilized onto different polymeric supports occurred at incubation pH value 7.5 and ADA concentration 42 units/g and the incubation time needed for the maximum amount of enzyme attachment to the polymeric supports was found to be 8 h. Some phsicochemical properties of the free and immobilized ADA such as operational stability, optimum temperature and thermal stability, pH optimum and stability, storage stability, and the effect of gamma-radiation were studied. The operational stability of the free and immobilized enzyme showed that the enzyme immobilized by a cross-linking technique using gultaric dialdehyde showed poor durability and the relative activity decreased sharply due to the leakage after repeated washing, while the enzymes immobilized by covalent bonds to the carriers showed a slight decrease in most cases in the relative activity (around 20%) after being used 10 times. Storage for 4-6 months, showed that the free enzyme lost its activity, while the immobilized enzyme showed the opposite behavior. Subjecting the immobilized enzyme to a dose of gamma radiation of 0.5-10 Mrad showed complete loss in the activity of the free enzyme at a dose of 5 Mrad, while the immobilized enzymes showed relatively high resistance to gamma radiation up to a dose of 5 Mrad.
other
2025-11-21 | Dupilumab for atopic manifestations in pediatric patients with inborn errors of immunity: efficacy and safety in a genetically diverse cohort
Background Inborn Errors of Immunity (IEI) are monogenic disorders that predispose patients to infections, autoimmunity, atopy, and malignancies. Severe Th2-driven atopic dermatitis and asthma are common in several IEIs, including DOCK8 deficiency, STAT3 loss-of-function, and Wiskott–Aldrich syndrome, often refractory to conventional therapies. Dupilumab, a monoclonal antibody targeting IL-4Rα, has shown promise in managing recalcitrant atopic dermatitis and asthma, but data in immunocompromised pediatric populations remain limited. Methods We conducted a single-center, retrospective observational cohort study with prospective follow-up of ten pediatric patients with genetically confirmed IEI and atopic manifestations. Patients received subcutaneous dupilumab (300 mg every 4 weeks for atopic dermatitis; every 2 weeks for severe asthma). Outcomes were assessed using the Eczema Area and Severity Index (EASI), Dermatology Life Quality Index (DLQI), Childhood Asthma Control Test (C-ACT), eosinophil counts, and infection frequency across four time points (baseline, 6 months, 12 months, >18 months). Results The cohort included ten patients (6 males, 4 females) with mutations in DOCK8 (n=5), CARD11 (n=2), STAT3 LOF (n=1), ADA (n=1), and PEPD (n=1). Of ten patients, nine received dupilumab for atopic dermatitis. Baseline EASI and DLQI scores were 34.33 and 25.0, respectively. Following dupilumab therapy, mean EASI decreased to 2.67 (p<0.001) and DLQI improved to 2.67 (p<0.001), with sustained response observed over 18 months. Peripheral eosinophil counts declined from 2.0×10 9 /L to 0.45×10 9 /L (p<0.001). One patient with severe asthma achieved C-ACT improvement from 10 to 26 with no subsequent exacerbations. Treatment was well-tolerated, with only mild conjunctivitis or transient hypereosinophilia reported. Notably, skin infections resolved, and no systemic or opportunistic infections were observed. Conclusion Dupilumab is a safe and highly effective therapeutic option for pediatric patients with IEI-associated atopic manifestations, improving clinical outcomes, quality of life, and infection profile while preserving immune function. These findings support broader application of dupilumab in patients with IEI and warrant further investigation in larger, multicenter studies.
2021-05-27 | Emapalumab treatment in an ADA-SCID patient with refractory hemophagocytic lymphohistiocytosis-related graft failure and disseminated bacillus Calmette-Guérin infection.
Emapalumab, a fully human anti-IFNγ monoclonal antibody, has been approved in the US as second-line treatment of primary hemophagocytic lymphohistiocytosis (HLH) patients and has shown promise in patients with graft failure (GF) requiring a second allogeneic hematopoietic stem cell transplantation (HSCT). The blockade of IFNγ activity may increase the risk of severe infections, including fatal mycobacteriosis. We report a case of secondary HLH-related GF in the context of HLA-haploidentical HSCT successfully treated with emapalumab in the presence of concomitant life-threatening infections, including disseminated tuberculosis (TB). A 4 years old girl with Adenosine Deaminase-Severe Combined Immunodeficiency complicated by disseminated TB came to our attention for ex-vivo hematopoietic stem cell-gene therapy. After engraftment failure of gene corrected cells, she received two HLA-haploidentical T-cell depleted HSCT from the father, both failed due to GF related to concomitant multiple infections and secondary HLH. Emapalumab administration allowed to control HLH, as well as to prevent GF after a third haplo-HSCT from the mother. Remarkably, all infections improved with antimicrobial medications and disseminated TB did not show any reactivation. This seminal case supports emapalumab use for treatment of secondary HLH and prevention of GF in patients undergoing haplo-HSCT even in the presence of multiple infections, including TB.
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Drug Discovery Landscape
6 orphan drug designations for Severe combined immunodeficiency due to adenosine deaminase deficiency, including 3 approved therapies.
6 orphan drug designations for Severe combined immunodeficiency due to adenosine deaminase deficiency, including 3 approved therapies.
Drug | Therapy type | Regulator | Orphan designation | Approval | Sponsor |
|---|---|---|---|---|---|
elapegademase-lvlr [Revcovi] | proteins | FDA | 2015-03-19 | 2018-10-05 | Chiesi USA Inc. |
autologous bone marrow CD34+ cells transduced ex vivo with a self activating HIV-1 -based lentiviral vector, EFS-ADA | gene therapies | FDA | 2014-10-21 | — | Donald B. Kohn, M.D. |
Autologous CD34+ cells transduced with a lentiviral vector containing the human ADA gene | gene therapies | EMA | 2013-06-07 | — | AdRes EU B.V. |
autologus CD34+ cells transfected with retroviral vector containing adenosine deaminase gene | gene therapies | FDA | 2009-08-26 | — | Fondazione Telethon ETS |
Autologous CD34+ cells transfected with retroviral vector containing adenosine deaminase gene [Strimvelis] | gene therapies | EMA | 2005-08-26 | 2016-05-30 | Fondazione Telethon Ets |
Pegademase bovine [Adagen] | proteins | FDA | 1984-05-29 | 1990-03-21 | Sigma-tau Pharmaceuticals, Inc. |
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