Verastem Oncology announces preliminary data from investigator-initiated study highlighting clinical activity of RAF/MEK and FAK combination in KRAS mutant tumours

The data will be presented as a virtual poster at the American Association for Cancer Research (AACR) 2020 Virtual Annual Meeting I.

This ongoing study is an open label, dose escalation and expansion study. The expansion cohorts are currently ongoing in patients with advanced solid tumors, including low-grade serous ovarian cancer (LGSOC), KRAS mutant non-small cell lung cancer (NSCLC) and KRAS mutant colorectal cancer (CRC). In the LGSOC cohort, among the patients with KRAS mutant tumors (n=6), 4 patients responded, for an overall response rate (ORR) of 67%. Median time on treatment was 20.5 months. In the KRAS mutant NSCLC cohort (n=10), 1 patient achieved a partial response and 8 patients achieved disease control. In this cohort, 70% of patients continued on treatment at least 12 weeks and 30% of patients continued on treatment at least 24 weeks.

Based on an observation of higher response rates seen in patients with KRASG12V mutations in the investigator-initiated Phase 1 combination study, we conducted a combined analysis with data from the combination study and the prior single-agent study that utilized a twice-weekly dosing schedule of VS-67661 to get a more complete picture of activity in KRASG12V mutations. The subsequent, combined analysis (VS-6766 monotherapy and defactinib combination) showed a 57% ORR (4/7 patients); as a single agent (2/5 patients) and in combination with defactinib (2/2 patients) in KRASG12V mutant NSCLC. Similarly, the combined analysis showed a 60% ORR (3/5 patients); as a single agent (1/2 patients) and in combination with defactinib (2/3 patients) in KRASG12V mutant gynecologic cancers. These additional analyses were conducted by Verastem Oncology to understand the impact that various KRAS variants may have had on response to identify potential signals to pursue in future prospective studies. This additional analysis was not part of the AACR 2020 poster presentation.

“Earlier research has demonstrated MEK inhibitors can cause upregulation of FAK in KRAS mutant tumors, which are notoriously difficult to treat and quite common across solid tumors. The combination of a RAF/MEK and FAK inhibitor can potentially overcome this challenge and opens up an exciting new pathway for treatment,” stated Professor Udai Banerji, Professor of Molecular Cancer Pharmacology at The Institute of Cancer Research, London, and Honorary Consultant in Medical Oncology, MBBS, MD, DNB, PhD, FRCP at The Royal Marsden NHS Foundation Trust, London, and lead investigator of the clinical study. “We found that the combination of VS-6766 and defactinib in low-grade serous ovarian cancer (LGSOC) was well tolerated by the patients in the trial and shows promising clinical activity, including durable response that is associated with clinically meaningful benefit. The study continues to enroll additional patients into the ovarian, lung and colorectal expansion cohorts with additional responses seen in all cohorts.”

“We are encouraged by these early response rates in KRAS mutant LGSOC and in KRASG12V mutant tumors as they underscore the significant potential of this novel approach in areas of high unmet medical need,” said Brian Stuglik, Chief Executive Officer of Verastem Oncology. “The potential of the combination of VS-6766 and defactinib is rapidly evolving as we continue to gain more insights and analyze the data. We plan to initiate discussions with regulatory authorities as soon as possible to define a path forward, with the goal of commencing a registration-directed clinical trial during 2020.”

Initial Results from the Phase 1 Study Investigating the Combination of VS-6766 and Defactinib in Patients with KRAS Mutant Cancers and Subsequent Analyses

The poster presentation describes safety and dose response data from the dose-escalation portion and expansion cohorts from an open-label, investigator-initiated Phase 1 study conducted in the United Kingdom assessing the combination of RAF/MEK and FAK inhibitor therapy in patients with LGSOC and KRAS mutant NSCLC. The study evaluated the combination of VS-6766 and defactinib. VS-6766 was administered using a twice-weekly dose escalation schedule and was administered 3 out of every 4 weeks. Defactinib was administered using a twice-daily dose escalation schedule, also 3 out of every 4 weeks. Dose levels were assessed in 3 cohorts: cohort 1 (VS-6766 3.2mg, defactinib 200mg); cohort 2a (VS-6766 4mg, defactinib 200mg); and cohort 2b (VS-6766 3.2mg, defactinib 400mg).

In the patients with LGSOC (n=8), the ORR was 50% (n=4). Among the patients with KRAS mutant LGSOC (n=6), the ORR was 67% (n=4). Of the 4 patients who have responded, 3 had a prior MEK inhibitor and as of November 2019 had been on study for a median of 20.5 months (range 7-23 months). In the patients with NSCLC (n=10), all of which had KRAS mutations, 1 patient achieved a partial response and 1 patient with a 22% tumor reduction still on treatment as of November 2019. Median time on treatment for this cohort was approximately 18 weeks.

Based on an observation of higher response rates seen in patients with KRASG12V mutations in the investigator-initiated Phase 1 combination study, we conducted a combined analysis with data from the combination study and the prior single-agent study that utilized a twice-weekly dosing schedule of VS-67661 to get a more complete picture of activity in KRASG12V mutations. The subsequent, combined analysis (VS-6766 monotherapy and defactinib combination) showed a 57% ORR (4/7 patients); as a single agent (2/5 patients) and in combination with defactinib (2/2 patients) in KRASG12V mutant NSCLC. Similarly, the combined analysis showed a 60% ORR (3/5 patients); as a single agent (1/2 patients) and in combination with defactinib (2/3 patients) in KRASG12V mutant gynecologic cancers. These additional analyses were conducted by Verastem Oncology to understand the impact that various KRAS variants may have had on response to identify potential signals to pursue in future prospective studies. This additional analysis was not part of the AACR 2020 poster presentation.

The most common side effects seen in the Phase 1 study were rash, creatine kinase elevation, nausea, hyperbilirubinemia and diarrhea, most being NCI CTC Grade 1/2 and all were reversible. The recommended Phase 2 dose was determined to be cohort 1 (VS-6766 3.2mg, defactinib 200mg).

The preliminary data reported in the study suggest that a novel intermittent dosing schedule of RAF/MEK and FAK inhibitor combination therapy has promising clinical activity in patients with KRAS mutant LGSOC and KRASG12V mutant NSCLC, including patients previously treated with a MEK inhibitor. Expansion cohorts remain ongoing.

Source: Company Press Release