2026-07-01 | Rethinking Locoregional Therapy of Merkel Cell Carcinoma in the Era of Immune Checkpoint Inhibition

Merkel cell carcinoma (MCC) is a highly aggressive yet profoundly immunotherapy-sensitive skin cancer characterized by early nodal and systemic dissemination. Historically, aggressive locoregional treatment was considered essential because therapeutic options for advanced disease were limited. The advent of immune checkpoint inhibitors has fundamentally transformed outcomes in MCC and, for the first time, enabled critical reassessment of established surgical and radiotherapeutic paradigms. Contemporary evidence suggests that intensified locoregional therapy does not consistently improve survival, which appears to be driven primarily by occult systemic disease. Emerging perioperative immunotherapy data therefore support more individualized, biology-driven strategies, including potential de-escalation of local therapy in selected patients while maintaining effective oncologic control.

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2026-07-01 | Atypical Grover Disease Associated With Merkel Cell Carcinoma: A Novel Paraneoplastic Presentation.

We report a case of atypical Grover disease occurring in association with Merkel cell carcinoma (MCC). A 63-year-old man presented with a four-month history of generalized pruritic papules. Skin biopsy demonstrated focal intraepidermal acantholysis with dyskeratosis and patchy vacuolar interface change, with negative direct immunofluorescence. Given the widespread eruption, systemic symptoms, and histopathologic findings, an atypical paraneoplastic variant of Grover disease was suspected. Four months later, the patient was diagnosed with metastatic MCC. His dermatologic disease improved with dupilumab and remained controlled during oncologic treatment. To our knowledge, this represents a previously unreported association between atypical Grover disease and MCC and raises the possibility of a paraneoplastic presentation.

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2026-07-01 | Targeted degradation of MDM2 overcomes feedback regulation of p53 signaling in Merkel cell carcinoma models.

MDM2 is transcriptionally activated by the ST-MYCL-Tip60 complex in virus-positive Merkel cell carcinoma (MCC). MDM2 suppresses p53 and is a rational therapeutic target. MDM2 inhibitors face an intrinsic limitation: p53 activation induces MDM2 transcription, creating a feedback loop that blunts inhibitor efficacy. We demonstrate that MDM2 degraders KTX-049 and KT-253 overcome this limitation by collapsing the p53/MDM2 negative feedback loop. KTX-049 was >100-fold more potent than the MDM2 inhibitor DS-3032 across WT p53 MCC cell lines, and this superior potency was quantitatively supported by mechanistic mathematical modeling. In vivo, KT-253 produced deep and durable tumor regressions, including complete responses in patient-derived xenograft models. Acquired resistance was strongly associated with acquisition of TP53 mutations, confirming on-target pathway pressure. These findings establish feedback architecture as a critical determinant of therapeutic response and position MDM2 degradation as a qualitatively distinct strategy that produces more durable pathway engagement than MDM2 inhibition, providing a preclinical rationale for prioritizing MDM2 degraders in WT TP53 MCC.

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