On Aprii 27, 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. RGENIX’s abstract, "RGX-104, a first-in-class immunotherapy targeting the liver-X receptor (LXR); Initial results from the phase 1b RGX-104 plus Docetaxel combination dose escalation cohorts" 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 (Press release, Rgenix, APR 27, 2020, View Source [SID1234556651]). The abstract results will be presented as a virtual poster presentation (CT-146) during the VPO.CT01 – Phase I Clinical Trials session on April 27, by clinical investigator Dr. Emerson Lim from Columbia University Herbert Irving Comprehensive Cancer Center, who is lead author on the study.
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For the dose escalation stage of this Phase 1b study, RGX-104 was tested in combination with docetaxel across three different dose escalation cohorts. The presentation will outline the safety profile, pharmacodynamic effects, and clinical activity of the combination in unselected heavily pre-treated patients with refractory or relapsed solid tumors. The results support further development of this regimen.
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, including docetaxel, providing a rationale for combination therapy with RGX-104. Consistent with this, RGX-104 plus docetaxel combination therapy is highly efficacious in pre-clinical models that demonstrate MDSC-associated docetaxel resistance.
As of February 7, 2020, 11 patients with refractory solid tumors were treated with the combination across 3 different dosing cohorts. The safety profile was consistent with the individual profiles of RGX-104 and docetaxel, with neutropenia the most common drug-related adverse event observed, but dose-limiting in only one patient in cohort one, where RGX-104 was administered at 80mg BID every day with docetaxel administered at 35mg/m2 weekly x 3. In cohorts two and three, in which patients received RGX-104 dosing five consecutive days out of seven (at either 80mg or 100mg BID) and a reduced dose of docetaxel (28mg/m2), no dose-limiting toxicity was observed, and sustained pharmacodynamic activity (ApoE activation and MDSC depletion) was achieved. The overall response rate (ORR) in all evaluable patients was 22%, with a disease control rate (DCR) of 56%. Across cohorts 2 and 3, where target RGX-104 pharmacodynamic effects were achieved, the ORR was 33% with a 67% DCR. Clinical responses included partial responses (PRs) in CPI refractory/resistant patients, including an ongoing confirmed PR in a CPI resistant melanoma patient treated in cohort 2 that remains on study at 10 months. Clinical activity was associated with increases in T cell activation markers exceeding that generally observed with RGX-104 alone.
As a result, the RGX-104/docetaxel regimen is being evaluated 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).
Emerson Lim, M.D., principal investigator from Columbia University Herbert Irving Comprehensive Cancer Center and lead author and presenter of the poster, said, "The clinical activity seen in the dose escalation of RGX-104 combined with Docetaxel is quite encouraging; especially notable is the ongoing PR of greater than 10 months duration in a patient with metastatic melanoma who had previously progressed with combination Nivolumab and Ipilimumab as his second line therapy. I am hopeful this combination will provide a therapeutic option for patients with ES-SCLC/HG-NET as currently being tested in the expansion phase."
RGX-104 is also 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).
Masoud Tavazoie, M.D., Ph.D., and Chief Executive Officer of RGENIX, said, "The data from the RGX-104/docetaxel combination dose escalation cohorts are encouraging, providing early safety and efficacy data that support further development of the combination. Though we are still in the early stages of the RGX-104 Phase 1b/2 studies, the results show the potential of RGX-104 to provide durable clinical activity in refractory patients through a novel mechanism-of-action. We look forward to sharing additional findings from these ongoing studies."