On May 29, 2025 Voltron Therapeutics, Inc., a Lucius Partners portfolio company, reported that data from Study VTX-IO-004 demonstrated clear proof-of concept for the self-assembling therapeutic, VTX-0P4, in the treatment of cancers over-expressing prostate stem cell antigen (PSCA) (Press release, Voltron Therapeutics, MAY 29, 2025, https://voltrontx.com/lucius-partners-portfolio-company-voltron-therapeutics-inc-announces-completion-of-a-trial-protocol-to-study-its-self-assembling-vaccine-to-target-prostate-stem-cell-antigen/ [SID1234654549]).
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VTX-0P4 is a novel, modular, protein-based therapy candidate designed to provide a specific therapeutic T cell mediated immunogenic response to PSCA-expressing tumors. Prior VTX-0P4 immunogenicity studies demonstrated robust overall antigen-specific T cell responses for both CD4+ and CD8+ T cell populations, in a murine model. PSCA is a critical marker in several primary cancers, including bladder, prostate, and pancreatic cancers.
The primary objective of study VTX-IO-004 was to evaluate the anti-tumor effect of VTX-0P4 in a well-established mouse model utilizing PSCA-expressing TRAMP-C2 (T-C2) tumors. A key secondary objective was to evaluate the anti-tumor effect of VTX-0P4 in combination with a checkpoint inhibitor (CPI). Treatment with VTX-0P4 induced robust, statistically significant antigen specific cellular immune responses and anti-tumor effects compared to controls. In addition, the combination of VTX-0P4 with a CPI demonstrated statistically highly significant additive efficacy benefit over VTX-0P4 or a CPI as monotherapy. This study provides further evidence supporting the utility of Voltron’s modular immunotherapeutic platform, demonstrating its ability to enhance targeted oncologic immune responses when combined with a well-established tumor associated antigen and a CPI.
These results add important potential indications to Voltron’s growing pipeline which includes HPV positive cervical and head and neck cancers.
Results of the study demonstrated:
Improved Overall Survival: VTX-0P4 + anti-mPD-1 had a highly significant, positive survival effect in the TC-1 tumor injected mice versus anti-mPD1 alone
Tumor volume reduction: VTX-0P4 + PD-1 significantly slowed/reduced growth in T-C2 tumor volume
Dose response: there was a clear dose-response to the combination which matched the previously reported immunogenicity results (i.e., the T cells are getting to their target)
Safety Profile: the SAV construct was well tolerated with no observed reactogenicity.
Dr. Mark Poznansky, a Scientific Founder of Voltron Therapeutics Inc and Director, Vaccine and Immunotherapy Center, MGH commented: "These data clearly demonstrate that this novel tumor targeting platform, when combined with a PD-1 inhibitor, significantly controlled tumor growth and augmented survival versus VTX-0P4 or a CPI alone. Additionally, these results are significant because it has now been shown that an effective cell mediated response against a self antigen, namely PSCA, can be generated by VTX-OP4. This supports the view that this novel self-assembling immunotherapy could be broadly applicable to a wide variety of cancers that are known to express tumor specific antigens."
Patrick J. Gallagher, Voltron’s Chief Executive Officer stated, "The results of this rigorously designed study highlight the great promise of Voltron’s platform technology. The VTX-0P4 responses, as measured by survival and tumor volume, were significantly enhanced when combined with a CPI / PD-1. Physiologically this makes sense. As the anti-mPD-1 removes the tumor’s ability to ‘escape’ the immune system, it creates a tumor microenvironment (TME) that’s more accessible to classic T cell-specific antitumor effects. Our approach activates and significantly increases the percentage of PSCA-specific antitumor T cells seeking to enter the TME, thus complementing the PD-1 inhibition mechanism of action."
This important research and development milestone further demonstrates and supports the therapy platform’s unique capabilities: utility in driving efficacy in combination therapy, development speed, target/pathogen flexibility and significant engagement of the immune system. This work with a full-length protein dramatically expands the breadth of potential value/solutions that the platform could offer in the oncology and infectious disease settings.
"Checkpoint inhibitors and other immunotherapies have dramatically improved outcomes for many cancer patients. Nonetheless there are still significant opportunities to improve patient outcomes through combination therapies with complimentary mechanisms," said James Ahern, Managing Partner of Laidlaw & Company and founder of Lucius Partners. "Our safety profile and compelling efficacy data could make us an ideal addition to current treatment algorithms. The Voltron team will continue to leverage our highly flexible platform to create new solutions for clinicians and patients and value for our shareholders."