On April 15, 2025 Toragen, Inc., a San Diego-based clinical-stage biotechnology company focused on developing uniquely selective drugs targeting cancers caused by viruses, reported positive safety data from its Phase 1 trial of TGN-S11, a small molecule inhibitor of the human papillomavirus (HPV) E5 oncogene protein, in patients with cancers associated with HPV (Press release, Toragen, APR 15, 2025, View Source [SID1234651951]).

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This Phase 1 trial was an open-label, non-randomized study in multiple cohorts of patients with relapsed, resistant, or metastatic HPV-associated cancers. The study has been conducted in two parts: Part 1 was escalating doses of TGN-S11 as monotherapy and Part 2 was TGN-S11 in combination with Keytruda (pembrolizumab), a PD-1 checkpoint inhibitor. The dose escalation part consisted of four Cohorts of three to six patients on monotherapy with increasing doses of TGN-S11. The Keytruda combination part consisted of three Levels of three to six patients with increasing doses of TGN-S11 and the standard dose of Keytruda.

In Part 1, 18 patients were treated with TGN-S11 as monotherapy in 4 dose cohorts with no serious adverse events identified. In the 4th dose cohort, 2 patients developed non-serious dose-related toxicities; therefore, the maximum tolerated dose (MTD) was determined to be 300mg/day. One-third of the patients who received TGN-S11 monotherapy showed drug activity with decreases in tumor size and decreases in Tumor Tissue Modified Viral (TTMV) HPV DNA as measured by the NavDx test. In addition, 10 patients were treated in Part 2 in 3 dose levels evaluating TGN-S11 in combination with Keytruda with no safety issues. Half of these patients in this portion of the study showed drug activity with decreases in tumor size and/or decreases in TTMV-HPV DNA score. One of these patients had a 92% reduction in TTMV-HPV DNA score and 3 patients remain on treatment.

This Phase 1 trial met both primary endpoints of proving safety and reaching the maximum tolerated dose of TGN-S11. In addition, our data also shows that 53% of patients that reached at least 2 months of treatment showed drug activity.

Dr. Neil Clendeninn, CMO of Toragen, said, "TGN-S11 was well-tolerated as monotherapy and in combination with Keytruda and we are very excited to see evidence of activity based on the reduction in TTMV-HPV DNA score in this study in advanced cancer patients."

Based on these positive results, Toragen plans to proceed with the development of its second-generation inhibitor of the E5 oncogene protein, TGN-S15, which has demonstrated increased efficacy and decreased side effects in preclinical testing. TGN-S15 will advance to IND-enabling studies to support a first in human study in healthy volunteers and Phase 2 clinical trials targeting HPV-associated cancers.