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Background/Objectives: Despite recent therapeutic advances, the clinical management of renal cell carcinoma (RCC) remains suboptimal. Current treatments are hindered by limited efficacy, the emergence of acquired drug resistance, suboptimal tolerability, and a lack of tumor-specific targeting. While development of novel agents remains an important avenue, it is often constrained by high costs, long development time, and low success rates. As an alternative approach, drug combinations of approved agents offer a promising strategy. Methods: Using our proprietary drug combination methodology, we identified multidrug combinations in RCC cells representing the clear cell (786O) and sarcomatoid chromophobe (UOK276) histological subtypes of RCC. Results: From an initial panel of 10 drugs, either approved or undergoing clinical trial, the optimized drug combinations (ODCs) contained crizotinib, telaglenastat, U-104, and vismodegib at clinical and subtherapeutic doses. The ODCs were non-toxic in advanced hepatic, renal, and cardiac cellular models. Importantly, their anti-tumor activity, already notable in normoxic (21% O2) conditions (approx. 50%) was markedly enhanced in tumor-relevant hypoxia (1.5% O2), reaching up to 77% in 2D and 62% in 3D spheroid 786O models. Moreover, chronic exposure of 786O and UOK276 cells led to durable responses, suggesting a prolonged effect in responders. Conclusions: Our findings demonstrate the potential of optimized, non-toxic drug combinations as a highly selective and effective strategy for accelerating the development of precision RCC treatment.

Multiple myeloma is a plasma cell malignancy with a poor prognosis despite the recent development of new therapeutic options. Histone deacetylase 6 (HDAC6) is overexpressed in multiple myeloma cells and may be involved in the acquisition of resistance to conventional anti-proteasome treatments. In addition to displaying a deacetylase catalytic activity, HDAC6 plays an essential role in the regulation of autophagy and cell death by recognizing ubiquitinated motifs from misfolded proteins through its C-terminal ZnF-UBP binding domain. These defective proteins are sent to the aggresome to facilitate their degradation by autophagy. Here, we explore the role of the ZnF-UBP binding domain of HDAC6 in the function of multiple myeloma cells. A non-functional ZnF-UBP domain containing a 2-residue mutation in the binding site was designed, and the absence of ubiquitin binding was confirmed in a cell-free assay. Molecular docking simulations and electrostatic calculations revealed a significant decrease in the electrostatic potential of the mutated peptide, which is crucial for the stability of the complex with ubiquitin. A multiple myeloma cell line containing the non-functional ZnF-UBP domain was then engineered. Although the deacetylase activity of HDAC6 was maintained in these cells, they showed reduced cell growth, impaired aggresome formation, and a dysregulated gene expression profile that was more pronounced than cells entirely deficient in HDAC6. These results indicate that a non-functional ZnF-UBP binding domain impacts the function of multiple myeloma cells. Based on these findings, a series of quinazolinylpropanoic acid derivatives was synthesized to explore the inhibitory activity of small molecules to this domain. We propose that ZnF-UBP binding domain inhibitors should be further evaluated as potential therapeutic agents in multiple myeloma.

Background Over the past two decades, most cancer vaccines have failed to be developed clinically. The lack of efficient priming with specific tumor antigens and/or weak adjuvants may explain this poor success rate. MVX-ONCO-1, a personalized cell-based vaccine, combines inactivated autologous tumor cells and encapsulated allogeneic human cells genetically engineered to produce granulocyte–macrophage colony stimulating factor (GM-CSF). This unique technology allows sustained local delivery of strong adjuvant at the vaccination site. The combination of inactivated autologous tumor cells and potent local adjuvant delivery addresses these two unmet critical steps and may recapitulate in patients the successful combination observed in experimental models. Methods The SAKK 11/16, a Phase IIa trial with Overall Survival (OS) as the primary endpoint was the first efficacy study evaluating MVX-ONCO-1. Patients with Recurrent/Metastatic Head and Neck Squamous Cell Carcinoma (R/M HNSCC) progressing after at least one line of systemic therapy were enrolled with 50% of patients alive at 26 weeks as the primary objective. Results In this hard-to-treat population, SAKK 11/16 met the primary endpoint, with 68.8% of patients alive at 6 months. The median OS was 11.4 months, with 32% of the patients alive after 18 months. Complete and partial responses were observed on MVX-ONCO-1 monotherapy. Moreover, all patients who developed a positive DTH reaction to their tumor cells upon vaccination survived at 12 months. Additionally, patients living for more than 12 months had higher circulating antibody titers against tumor-associated antigens. Explorative analysis looking at median OS from the start of anti-PD-1 therapy was 21.7 months. In addition, no new safety signals with no systemic adverse events (AE) related to the treatment and no manufacturing issues were observed in this multicenter trial. Conclusions These findings suggest that MVX-ONCO-1 can induce a coordinated immune response with clinical benefits as a standalone treatment, leading to prolonged survival. This effect may be enhanced by previous exposure to immune checkpoint inhibitors. Trial registration (ClinicalTrials.gov): NCT02999646.

Multiple myeloma is a plasma cell malignancy with poor prognosis despite the recent development of new therapeutic options. Histone deacetylase 6 (HDAC6) is overexpressed in multiple myeloma patients and may be involved in the acquisition of resistance to conventional anti-proteasome treatments. Beyond displaying a deacetylase catalytic activity, HDAC6 can recognize ubiquitinated motifs from misfolded proteins through its C-terminal ZnF-UBP binding domain and send the defective proteins to the aggresome for degradation. Here, we explore the role of the ZnF-UBP binding domain of HDAC6 in the function of multiple myeloma cells. A non-functional ZnF-UBP domain containing a 2-residue mutation in the binding site was designed and the absence of ubiquitin binding was confirmed in a cell-free assay. Molecular docking simulations and electrostatic calculations revealed a significant decrease in the electrostatic potential of the mutated peptide, which is crucial for the stability of the complex with ubiquitin. A multiple myeloma cell line containing the non-functional ZnF-UBP domain was then engineered. Although the deacetylase activity of HDAC6 was maintained in these cells, they showed reduced cell growth, impaired aggresome formation and a dysregulated gene expression profile that was more pronounced than cells entirely deficient in HDAC6. These results indicate that a non-functional ZnF-UBP binding domain impacts the function of multiple myeloma cells. Based on these findings, a series of quinazolinylpropanoic acid derivatives was synthesized to explore the inhibitory activity of small molecules to this domain. We propose that ZnF-UBP binding domain inhibitors should be further evaluated as potential therapeutic agents in multiple myeloma.

Hydrogen sulfide (H₂S) is a redox-active gasotransmitter implicated in tumor progression and immune regulation. The enzyme 3-mercaptopyruvate sulfurtransferase (3-MST) is a key contributor to endogenous H₂S and polysulfide production, but its role in tumor–immune interactions remains poorly defined. Here, we show that 3-MST is the most abundantly expressed H₂S-synthesizing enzyme in human renal cell carcinoma cells (RCC) and that high 3-MST expression correlates with reduced patient survival. Pharmacological inhibition of 3-MST lowered intracellular H₂S levels in Renca renal carcinoma cells, suppressed proliferation, induced apoptosis, and increased surface expression of the immunogenic markers CD70, CD86, and PD-L1. In immune cells, partial inhibition of 3-MST promoted T cell activation, as evidenced by increased CD69 expression on both CD4⁺ helper and CD8⁺ cytotoxic T cells. In contrast, complete inhibition of 3-MST, achieved by high concentrations of the inhibitor, modestly reduced CD8⁺ T cell proliferation. Functionally, 3-MST inhibition potentiated antigen-specific CD8⁺ T cell-mediated killing of tumor cells, an effect further amplified by PD-L1 blockade. These results establish 3-MST as a redox-sensitive metabolic driver of tumor growth and immune evasion in RCC and demonstrate that its inhibition can boost antitumor immune responses, offering a potential avenue for combination immunotherapy.