There is an urgent need to develop treatments for patients with melanoma who are refractory to or ineligible for immune checkpoint blockade, including patients who lack BRAF-V600E/K mutations. This is often the case in patients diagnosed with rare melanoma subtypes such as mucosal and acral melanoma. Here, we analyzed data from the cutaneous melanoma The Cancer Genome Atlas Network (TCGA) transcriptomic and proteomic databases for differential expression of apoptosis molecules between melanomas with or without BRAF hotspot mutations. Our data indicated higher B-cell CLL/lymphoma 2 (BCL2) expression in melanoma without BRAF hotspot mutations, suggesting that BH3 mimetics, such as ABT-199 (venetoclax, a small molecule against BCL2), may be a potential therapeutic option for these patients. We explored the efficacy of combining two BH3 mimetics, ABT-199 and a myeloid cell leukemia sequence 1 (MCL1) inhibitor (S63845 or S64315/MIK665) in cutaneous, mucosal and acral melanomas, in vitro and in vivo. Our data indicate this combination induced cell death in a broad range of melanoma cell lines, including melanoma initiating cell populations, and was more potent in melanoma cells without BRAF-V600E/K mutations. Our knockdown/knockout experiments suggest that several pro-apoptotic BCL2 family members, BCL2-like 11 (apoptosis facilitator) (BIM), phorbol-12-myristate-13-acetate-induced protein 1 (NOXA) or BID, play a role in the combination-induced effects. Overall, our study supports the rationale for combining an MCL1 inhibitor with a BCL2 inhibitor as a therapeutic option in patients with advanced melanoma.

The BCL2 family of proteins plays a pivotal role in regulating apoptosis and cellular homeostasis, making them critical therapeutic targets in cancer and other diseases characterized by pathological cell survival. BH3 mimetics, small molecules that selectively inhibit anti-apoptotic BCL2 family members, have achieved significant clinical success, particularly in hematologic malignancies. However, several challenges remain, including resistance mechanisms, toxicity (such as MCL1 inhibitor-associated cardiotoxicity), and the intricate balance between apoptotic and non-apoptotic functions. This review provides a comprehensive overview of BCL2 family biology, the development and clinical application and outcomes of BH3 mimetics, and the emerging resistance mechanism known as double-bolt locking. We also examine strategies to overcome resistance, including combination therapies and immunomodulatory approaches. Beyond oncology, we highlight the expanding therapeutic potential of BH3 mimetics in autoimmune, fibrotic, and infectious diseases, as well as regenerative and anti-aging medicine. Finally, we discuss predictive biomarkers and tissue-specific responses that inform precision therapy. Together, these insights underscore the promise of BH3 mimetics and the need for continued multidisciplinary research to optimize their clinical impact.

Although treatment options for melanoma patients have expanded in recent years with the approval of immunotherapy and targeted therapy, there is still an unmet need for new treatment options for patients that are ineligible for, or resistant to these therapies. BH3 mimetics, drugs that mimic the activity of pro-apoptotic BCL2 family proteins, have recently achieved remarkable success in the clinical setting. The combination of BH3 mimetic ABT-199 (venetoclax) plus azacitidine has shown substantial benefit in treating acute myelogenous leukemia. We evaluated the efficacy of various combinations of BH3 mimetic + azacitidine in fourteen human melanoma cell lines from cutaneous, mucosal, acral and uveal subtypes. Using a combination of cell viability assay, BCL2 family knockdown cell lines, live cell imaging, and sphere formation assay, we found that combining inhibition of MCL1, an anti-apoptotic BCL2 protein, with azacitidine had substantial pro-apoptotic effects in multiple melanoma cell lines. Specifically, this combination reduced cell viability, proliferation, sphere formation, and induced apoptosis. In addition, this combination is highly effective at reducing cell viability in rare mucosal and uveal subtypes. Overall, our data suggest this combination as a promising therapeutic option for some patients with melanoma and should be further explored in clinical trials.