On June 22, 2020 RGENIX, Inc., a clinical stage biopharmaceutical company developing first-in-class small molecule and antibody cancer therapeutics, reported it is presenting an abstract on RGX-104, RGENIX’s lead therapy in development (Press release, Rgenix, JUN 22, 2020, View Source [SID1234561349]). RGENIX’s abstract, "Correlative analysis of pharmacokinetics and pharmacodynamics of RGX-104, a first-in-class Liver-X-Receptor (LXR) agonist, and clinical outcomes in patients with advanced solid tumors" was accepted for the 2020 American Association for Cancer Research (AACR) (Free AACR Whitepaper) Annual Meeting, which this year was scheduled as two virtual meetings. The abstract results will be presented as a virtual poster presentation (#LB-133/7) in the Late-Breaking Research: Clinical Research 1 session on June 22, by clinical investigator Dr. Monica Mita, Co-Director, Experimental Therapeutics Program, Samuel Oschin Comprehensive Cancer Institute at Cedars-Sinai Medical Center, who is lead author on the study.

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RGX-104 is a small-molecule LXR agonist that modulates innate immunity via transcriptional activation of the ApoE gene. RGX-104 inhibits tumor angiogenesis and depletes myeloid derived suppressor cells (MDSC), thereby activating cytotoxic T-lymphocytes. MDSCs are associated with resistance to both checkpoint inhibitors (CPI) and chemotherapy, providing a rationale for combination therapy with RGX-104.

For the dose escalation stage of the Phase 1 study, RGX-104 was tested as a monotherapy or in combination with either nivolumab, ipilimumab, or docetaxel in heavily pre-treated patients with refractory or relapsed solid tumors, including patients who had progression on prior checkpoint inhibitors (CPI). As outlined in the presentation, objective clinical activity was observed in all treatment arms, including the monotherapy arm, with partial responses achieved in patients with NSCLC, SCLC, melanoma, SCCHN, and endometrial cancer.

Of note, in the combination arms, a 28.6% objective response rate was observed in all evaluable patients who had previously progressed on CPI, with 4 of 14 evaluable patients achieving PRs. Responses included ongoing durable PRs – some exceeding 11 months – in CPI refractory/resistant patients whose tumors were PD-L1 low/negative.

Importantly, clinical activity across all treatment arms was associated with RGX-104 related pharmacodynamic effects, including ApoE activation, MDSC depletion, and CD8 T cell activation with associated induction of IFNγ. Robust ApoE induction was achieved with BID dosing of RGX-104 and was correlated with the magnitude of MDSC depletion. Additionally, in comparison to PD-L1 positive tumors, PD-L1 negative tumors were found to have significantly lower baseline (pre-treatment) levels of ApoE, a feature associated with higher likelihood of clinical benefit to RGX-104. The data demonstrate that MDSC depletion via ApoE induction with RGX-104 can overcome resistance to CPI or chemotherapy, resulting in durable clinical activity.

As a result, RGX-104 is being evaluated in combination with the front-line standard-of-care regimen of pembrolizumab plus carboplatin/pemetrexed in a phase 1b/2 study currently enrolling patients with advanced non-squamous non-small cell lung cancer (NSCLC) whose tumors are PD-L1 negative. RGX-104 is also being evaluated in combination with docetaxel in a phase 1b/2 expansion study that has begun enrolling patients with relapsed/refractory extensive stage small-cell lung cancer (ES-SCLC) or high grade-neuroendocrine tumors (HG-NET).

Monica Mita, M.D., principal investigator from Cedars-Sinai Medical Center and lead author and presenter of the poster, said, "These exciting results provide clinical validation of the novel MDSC-targeting mechanism of RGX-104. The durable clinical responses observed in patients who have previously progressed on checkpoint inhibitors are very promising."

Masoud Tavazoie, M.D., Ph.D., and Chief Executive Officer of RGENIX, said, "We are very encouraged by the results presented today as they demonstrate that our first-in-class drug candidate RGX-104 can robustly target MDSCs, a key drug resistance mechanism, to provide durable clinical benefit to patients. The findings further strengthen the foundation for our ongoing Phase 1b/2 studies. We look forward to sharing results from these ongoing studies."