Arvinas Releases Updated Dose Escalation Data from Clinical Trial of PROTAC Protein Degrader ARV-110 in Patients with Metastatic Castration-Resistant Prostate Cancer - Seite 2

ARV-110 has demonstrated evidence of activity at doses and in AR mutational backgrounds in which responses would be expected based on preclinical data. As of the April 20, 2020 data cut-off, 20 patients were evaluable for prostate-specific antigen (PSA) response, including 12 patients treated at 140 mg or higher (these 12 patients exclude one patient who received two weeks of therapy prior to discontinuing due to a rosuvastatin-related dose limiting toxicity).

Of those 12 patients treated at 140 mg and above, circulating tumor DNA (ctDNA) analysis of five patients showed AR forms not degradable by ARV-110 in preclinical studies (i.e., L702H point mutations and AR-V7 splice variants). In the group of seven remaining patients who had forms of AR degradable by ARV-110 (other AR point mutations, AR amplification, and wildtype AR), two patients achieved confirmed PSA responses that remain ongoing with additional follow-up since the abstract was submitted.

One of these patients had a 74% decline from baseline in PSA and remained without progression after 30 weeks, as of the data cut-off. This patient did not have measurable disease at baseline for assessment by Response Evaluation Criteria in Solid Tumors (RECIST). The second patient had both a deep PSA response (97% decline from baseline) and a confirmed RECIST response (80% decrease from baseline in tumor mass) and remains without progression after 18 weeks. Both responses, which were in patients at the 140 mg dose, were achieved by ARV-110 despite prior enzalutamide, abiraterone, chemotherapy, and other therapies. Tumors from both patients have H875Y and T878A point mutations in AR, which are known to drive resistance to current standard of care treatments and have been degraded by ARV-110 in preclinical studies. In addition to these two patients, PSA reductions were observed in other patients but did not meet a 50% reduction in PSA threshold at data cutoff, and four patients remain on ARV-110 without radiographic progression for at least 20 weeks.

A potential drug-drug interaction between ARV-110 and rosuvastatin (ROS) was identified during the trial. Of the 22 patients enrolled, two had concurrent use of ROS. One patient receiving 280 mg ARV-110 experienced a Grade 4 dose-limiting toxicity (DLT) of elevated aspartate transaminase/alanine transaminase (AST/ALT) followed by acute renal failure. The second patient, receiving 70 mg ARV-110, experienced a Grade 3 AST/ALT elevation, which resolved after the removal of ROS, and the patient was retreated with ARV-110. Follow-up exploratory findings indicate that ROS concentrations were elevated in both patients who had liver function test (LFT) increases. Subsequent in vitro transport pump studies indicate that ARV-110 inhibits breast cancer resistant pump (BCRP) transporter, of which ROS is a substrate. Following the initial data that supported a potential interaction with ROS, concomitant use of ROS was precluded, and no other related Grade 3 or 4 adverse events have since been reported. Six other patients have received concomitant non-ROS statins without AST/ALT adverse events.