RARE DISEASE
Vitamin B12-responsive methylmalonic acidemia
Vitamin B12-responsive methylmalonic acidemia
Vitamin B12-responsive methylmalonic acidemia
Synonyms: Adenosylcobalamin deficiency, Vitamin B12-responsive methylmalonic aciduria
Synonyms: Adenosylcobalamin deficiency, Vitamin B12-responsive methylmalonic aciduria
Synonyms: Adenosylcobalamin deficiency, Vitamin B12-responsive methylmalonic aciduria
Drug discovery
1
drug
With orphan designation
Overview
Vitamin B12-responsive methylmalonic acidemia (MMA) is an inborn error of cobalamin metabolism caused by impaired adenosylcobalamin synthesis, leading to toxic methylmalonic acid accumulation. It presents with ketoacidosis, dehydration, hypotonia, developmental delay, and metabolic strokes. Three subtypes exist (cblA, cblB, and cblDv2), distinguished by genetic mutations (MMAA, MMAB, and MMADHC genes). Diagnosis relies on elevated MMA levels and genetic testing. Early vitamin B12 therapy improves outcomes, particularly in cblA and some cblB cases [1][2][4][10].
Burden
Neurological sequelae (intellectual disability, metabolic strokes) in 30–60% [2][9].
Mortality: 25–50% in untreated cases, with lifelong management required [5][6].
Vitamin B12 responsiveness correlates with prognosis, with cblA patients often achieving near-normal development under therapy [1][7]. Regular monitoring for renal and neurological complications is critical [4][6].
Categories: rare genetic diseases, rare inborn errors of metabolism, rare renal diseases, rare transplant-related disorders
Research Papers
163 drug discovery papers about Vitamin B12-responsive methylmalonic acidemia, with 3 first-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
163 drug discovery papers about Vitamin B12-responsive methylmalonic acidemia, with 3 first-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
2025-12-18 | Afg3l2 couples mitochondrial vitamin B12 trafficking to amino acid metabolism to safeguard hematopoietic stem cell homeostasis.
Mitochondrial proteostasis is essential for hematopoietic stem cell (HSC) maintenance, yet how proteolytic regulation coordinates with metabolic pathways remains unclear. Here, we identify Afg3l2 as a key regulator of cobalamin metabolism and amino acid homeostasis in HSCs through its mediation of Mmadhc degradation. Loss of Afg3l2 leads to Mmadhc accumulation, driving excessive mitochondrial cobalamin import and its conversion to adenosylcobalamin. Elevated adenosylcobalamin levels hyperactivate methylmalonyl-CoA mutase, diverting branched-chain amino acid catabolism toward excessive succinyl-CoA production. This overstimulates the tricarboxylic acid cycle and creates a compensatory dependency on anaplerotic amino acid replenishment. Consequently, Afg3l2-deficient HSCs exhibit increased oxidative stress due to mitochondrial hyperactivation and reactive oxygen species accumulation, ultimately impairing their maintenance and engraftment capacity. Remarkably, Mmadhc overexpression phenocopies these defects, whereas Mmadhc knockdown partially restores HSC function in Afg3l2-deficient models. Our work defines a proteostatic-metabolic circuit in which Afg3l2-mediated Mmadhc degradation regulates cobalamin flux to maintain amino acid and energy balance in HSCs.
2025-09-09 | Immunostimulatory and Immunomodulatory Effects of Vitamin B12 Derivatives on Macrophages Through the Modulation of JNK Pathway.
Vitamin B12 is a vital water-soluble vitamin containing a central cobalt atom within its corrin ring structure. It exists in several derivatives, among which methylcobalamin (MeCbl) and adenosylcobalamin (AdCbl) are the biologically active forms that serve as cofactors in essential enzymatic reactions. Although the neurological and hematological consequences of vitamin B12 deficiency have been extensively studied, its role in immune regulation remains less well understood. Considering that macrophages are key effector cells of innate immunity, this study aimed to investigate the immunostimulatory and immunomodulatory properties of MeCbl and AdCbl on murine macrophages (J774.2 cell line) with a particular focus on cytokine responses and the JNK signaling pathway. Macrophages were cultured under controlled conditions and treated with non-cytotoxic concentrations of MeCbl and AdCbl (1, 5, and 10 µg/mL), either alone or in combination with lipopolysaccharide (LPS, 1 µg/mL) as a pro-inflammatory stimulus. Cell viability was first confirmed using Trypan Blue exclusion to ensure that the tested concentrations did not impair cellular survival. Supernatants were then analyzed for cytokine production (TNF-α, IL-6, IL-12p40, GM-CSF) using ELISA, and intracellular signaling was investigated through flow cytometric analysis of phosphorylated JNK (p-JNK) levels. The results revealed that under non-inflammatory conditions, neither MeCbl nor AdCbl significantly altered cytokine production, suggesting a lack of direct immunostimulatory activity in resting macrophages. However, in the presence of LPS, both derivatives markedly increased TNF-α levels, consistent with enhanced pro-inflammatory activation. At the same time, both compounds significantly suppressed IL-6 and IL-12p40 production, pointing to their capacity to counterbalance excessive Th1-driven responses. Importantly, AdCbl demonstrated a unique, concentration-dependent reduction in GM-CSF levels, whereas MeCbl induced only minimal and inconsistent changes, indicating that AdCbl exerts a more selective regulatory profile while MeCbl has broader but less concentration-dependent effects. Flow cytometry further confirmed that both derivatives strongly enhanced JNK phosphorylation, implicating this signaling pathway as a mechanistic link between vitamin B12 derivatives and cytokine modulation. Taken together, these findings demonstrate that MeCbl and AdCbl exert distinct yet overlapping immunomodulatory effects in macrophages. By simultaneously promoting TNF-α while limiting IL-6, IL-12p40, and GM-CSF (for AdCbl), these compounds display a complex balance of pro- and anti-inflammatory activities mediated, at least in part, through the JNK pathway. This dual role highlights their potential relevance in fine-tuning immune responses, preventing excessive inflammation, and supporting host defense. The study provides new insights into the immunological functions of vitamin B12 derivatives and suggests that future research should explore their therapeutic applications in immune-related disorders and inflammatory diseases.
2025-06-18 | A case report of combined methylmalonic acidemia and homocysteinemia presented with cerebral sinus thrombosis and fluctuating cognitive impairment.
MMACHC deficiency leads to combined methylmalonic acidemia and homocysteinemia. The disease is characterized by the presence of methylmalonic acidemia and hyperhomocysteinemia, leading to widespread clinical manifestations affecting multiple organs. Due to the low incidence of cblC deficiency and the diversity of its clinical phenotypes, diagnosis was challenging and often results in delays or missed diagnoses. We now report a case of a male patient who experienced fluctuating cognitive impairment and headaches for 3 times. He was initially diagnosed with encephalitis and venous sinus thrombosis, but his symptoms recurred. Later, significantly elevated levels of homocysteine and methylmalonic acid were detected. Genetic analysis confirmed the presence of a heterozygous mutation in the MMACHC gene, establishing the definitive diagnosis. This case is reported due to its rarity and diverse clinical presentations, highlighting the need for increased awareness of this condition. A male patient exhibited recurrent episodes of fluctuating cognitive impairment and headaches. The patient underwent magnetic resonance imaging, lumbar puncture, and cerebrospinal fluid analysis. To confirm the diagnosis, genetic sequencing analysis was also conducted. In terms of intervention, the patient received supplementation with cobamamide, vitamin B1, and folic acid, leading to gradual relief and improvement of symptoms. The patient's headaches and cognitive impairment symptoms have alleviated, and there have been no recurrences during follow-up. To our knowledge, there are few clinical cases of methylmalonic acidemia presenting primarily with episodic cognitive impairment and venous sinus thrombosis. Therefore, it is essential to enhance the recognition and differential diagnosis of such symptoms to improve the accuracy and speed of the disease diagnosis.
2025-12-18 | Afg3l2 couples mitochondrial vitamin B12 trafficking to amino acid metabolism to safeguard hematopoietic stem cell homeostasis.
Mitochondrial proteostasis is essential for hematopoietic stem cell (HSC) maintenance, yet how proteolytic regulation coordinates with metabolic pathways remains unclear. Here, we identify Afg3l2 as a key regulator of cobalamin metabolism and amino acid homeostasis in HSCs through its mediation of Mmadhc degradation. Loss of Afg3l2 leads to Mmadhc accumulation, driving excessive mitochondrial cobalamin import and its conversion to adenosylcobalamin. Elevated adenosylcobalamin levels hyperactivate methylmalonyl-CoA mutase, diverting branched-chain amino acid catabolism toward excessive succinyl-CoA production. This overstimulates the tricarboxylic acid cycle and creates a compensatory dependency on anaplerotic amino acid replenishment. Consequently, Afg3l2-deficient HSCs exhibit increased oxidative stress due to mitochondrial hyperactivation and reactive oxygen species accumulation, ultimately impairing their maintenance and engraftment capacity. Remarkably, Mmadhc overexpression phenocopies these defects, whereas Mmadhc knockdown partially restores HSC function in Afg3l2-deficient models. Our work defines a proteostatic-metabolic circuit in which Afg3l2-mediated Mmadhc degradation regulates cobalamin flux to maintain amino acid and energy balance in HSCs.
2025-09-09 | Immunostimulatory and Immunomodulatory Effects of Vitamin B12 Derivatives on Macrophages Through the Modulation of JNK Pathway.
Vitamin B12 is a vital water-soluble vitamin containing a central cobalt atom within its corrin ring structure. It exists in several derivatives, among which methylcobalamin (MeCbl) and adenosylcobalamin (AdCbl) are the biologically active forms that serve as cofactors in essential enzymatic reactions. Although the neurological and hematological consequences of vitamin B12 deficiency have been extensively studied, its role in immune regulation remains less well understood. Considering that macrophages are key effector cells of innate immunity, this study aimed to investigate the immunostimulatory and immunomodulatory properties of MeCbl and AdCbl on murine macrophages (J774.2 cell line) with a particular focus on cytokine responses and the JNK signaling pathway. Macrophages were cultured under controlled conditions and treated with non-cytotoxic concentrations of MeCbl and AdCbl (1, 5, and 10 µg/mL), either alone or in combination with lipopolysaccharide (LPS, 1 µg/mL) as a pro-inflammatory stimulus. Cell viability was first confirmed using Trypan Blue exclusion to ensure that the tested concentrations did not impair cellular survival. Supernatants were then analyzed for cytokine production (TNF-α, IL-6, IL-12p40, GM-CSF) using ELISA, and intracellular signaling was investigated through flow cytometric analysis of phosphorylated JNK (p-JNK) levels. The results revealed that under non-inflammatory conditions, neither MeCbl nor AdCbl significantly altered cytokine production, suggesting a lack of direct immunostimulatory activity in resting macrophages. However, in the presence of LPS, both derivatives markedly increased TNF-α levels, consistent with enhanced pro-inflammatory activation. At the same time, both compounds significantly suppressed IL-6 and IL-12p40 production, pointing to their capacity to counterbalance excessive Th1-driven responses. Importantly, AdCbl demonstrated a unique, concentration-dependent reduction in GM-CSF levels, whereas MeCbl induced only minimal and inconsistent changes, indicating that AdCbl exerts a more selective regulatory profile while MeCbl has broader but less concentration-dependent effects. Flow cytometry further confirmed that both derivatives strongly enhanced JNK phosphorylation, implicating this signaling pathway as a mechanistic link between vitamin B12 derivatives and cytokine modulation. Taken together, these findings demonstrate that MeCbl and AdCbl exert distinct yet overlapping immunomodulatory effects in macrophages. By simultaneously promoting TNF-α while limiting IL-6, IL-12p40, and GM-CSF (for AdCbl), these compounds display a complex balance of pro- and anti-inflammatory activities mediated, at least in part, through the JNK pathway. This dual role highlights their potential relevance in fine-tuning immune responses, preventing excessive inflammation, and supporting host defense. The study provides new insights into the immunological functions of vitamin B12 derivatives and suggests that future research should explore their therapeutic applications in immune-related disorders and inflammatory diseases.
2025-06-18 | A case report of combined methylmalonic acidemia and homocysteinemia presented with cerebral sinus thrombosis and fluctuating cognitive impairment.
MMACHC deficiency leads to combined methylmalonic acidemia and homocysteinemia. The disease is characterized by the presence of methylmalonic acidemia and hyperhomocysteinemia, leading to widespread clinical manifestations affecting multiple organs. Due to the low incidence of cblC deficiency and the diversity of its clinical phenotypes, diagnosis was challenging and often results in delays or missed diagnoses. We now report a case of a male patient who experienced fluctuating cognitive impairment and headaches for 3 times. He was initially diagnosed with encephalitis and venous sinus thrombosis, but his symptoms recurred. Later, significantly elevated levels of homocysteine and methylmalonic acid were detected. Genetic analysis confirmed the presence of a heterozygous mutation in the MMACHC gene, establishing the definitive diagnosis. This case is reported due to its rarity and diverse clinical presentations, highlighting the need for increased awareness of this condition. A male patient exhibited recurrent episodes of fluctuating cognitive impairment and headaches. The patient underwent magnetic resonance imaging, lumbar puncture, and cerebrospinal fluid analysis. To confirm the diagnosis, genetic sequencing analysis was also conducted. In terms of intervention, the patient received supplementation with cobamamide, vitamin B1, and folic acid, leading to gradual relief and improvement of symptoms. The patient's headaches and cognitive impairment symptoms have alleviated, and there have been no recurrences during follow-up. To our knowledge, there are few clinical cases of methylmalonic acidemia presenting primarily with episodic cognitive impairment and venous sinus thrombosis. Therefore, it is essential to enhance the recognition and differential diagnosis of such symptoms to improve the accuracy and speed of the disease diagnosis.
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Drug Discovery Landscape
1 orphan drug designation for Vitamin B12-responsive methylmalonic acidemia.
1 orphan drug designation for Vitamin B12-responsive methylmalonic acidemia.
Drug | Therapy type | Regulator | Orphan designation | Approval | Sponsor |
|---|---|---|---|---|---|
recombinant adeno-associated viral vector with human methylmalonyl-COA mutase (MUT) gene | gene therapies | FDA | 2019-04-22 | — | LogicBio Therapeutics, Inc. |
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