Safety, tolerability, and preliminary efficacy of tinodasertib as a monotherapy or in combination with pembrolizumab or irinotecan in metastatic colorectal cancer: Interim results from a phase II open-label, dose-finding, run-in and cohort expansion

183 Background: MNK inhibition has been shown to downregulate phosphorylation at serine 209 of eIF4E, a potent regulatory point of CAP-mediated translation of 5’ polyadenylated mRNA associated with growth factor and pro-oncogenic signals in cells. Elevated levels of eIF4E phosphorylation are observed in a broad range of tumors. MNK1/2 knock out mice are healthy and viable, as cellular house-keeping mRNA translation occurs readily using the IRES mechanism, whereas mRNA with more complex and longer 5’ untranslated ends such as those involved in growth factor and pro-oncogenic signaling, are MNK activated. Cells from MNK knockout animals become relatively resistant to subsequent oncogenic transformation. In a program of SAD and MAD Phase I studies conducted in normal healthy volunteers, Tinodasertib was found to be safe and well tolerated with no dose-limiting toxicity (DLT). The objectives of this ongoing Phase 2 study are to evaluate safety, and preliminary efficacy of Tinodasertib as monotherapy and in combination with either pembrolizumab or irinotecan in patients with advanced colorectal cancer (CRC). Methods: Patients had to have advanced CRC and previously received ≥2 lines of therapy. The dose escalation phase of the study was open to all patients with CRC. As of 23 July 2024, 22 patients were dosed in a modified 3X3 dose escalation design with Tinodasertib from 20 to 80 mg on alternate days. Out of 22 patients, 12 received monotherapy, 4 were treated with Tinodasertib and Irinotecan and 6 were treated with Tinodasertib and pembrolizumab. Majority (19) had MSS CRC and 3 had unknown status. Nine patients had KRAS-mut CRC. Results: No DLTs were observed and MTD was not reached. Grade 3 treatment-related adverse events (TRAEs) were observed in 2 (9%) patients and were related to irinotecan while no Grade 3 AEs were attributed to Tinodasertib by either the investigator or the sponsor. Most common TRAEs were related to gastrointestinal system organ class. There were no Grade 4-5 TRAEs. Of the 22 patients, 18 were evaluable for RECIST 1.1 response. No patient had an objective response to treatment, 12 had stable disease with disease control rate of 67% and a progression free survival of 2.99 months. Patients remained on therapy for up to 28 weeks. Overall survival (OS) at 52 weeks was 52% (CI 29 to 93). Conclusions: Tinodasertib either as monotherapy or combined with irinotecan or pembrolizumab, was well tolerated with no DLTs at the dose levels evaluated. Prolonged median time to progression and OS compared to historical controls were observed even during the dose escalation phase for the study population as a whole and for each of the monotherapy and combination arms. Enrolment in the dose escalation phase continues. Clinical trial information: NCT05462236 .