Updated design of INVOKE: A phase 1 study of OKN4395, a first-in-class EP2/EP4/DP1 triple prostanoid receptor antagonist, in patients with advanced solid tumors.

Abstract

TPS2681 Background: The immunosuppressive pathway of prostaglandin E 2 (PGE 2 ), part of the cyclooxygenase (COX) pathway, is upregulated in certain cancers and has been implicated in tumor evasion of CD8 T, NK, and dendritic immune cells, allowing tumor growth and metastasis (Jin et al., 2023). COX2 inhibitors, aspirin and nonsteroidal anti-inflammatories (NSAIDS) have shown some survival benefit in patients with gastrointestinal cancer and others (Cao et al., 2016; Martling et al., 2025; Takiuchi et al., 2018; Zhang et al., 2025); however, results are inconsistent, likely due to toxicity limiting complete blockade of the pathway, highlighting the need for more potent but selective inhibitors. OKN4395 is a first-in-class, highly selective, equipotent inhibitor of EP2, EP4, and DP1, downstream receptors for COX-derived PGE 2 , and PGD 2 , respectively. DP1 has described roles in immunosuppression and inhibition of apoptosis, supporting the therapeutic rationale (Luo et al., 2024; Peinhaupt et al., 2017). OKN4395 is hypothesized to modulate the tumor microenvironment to allow an effective immune response as monotherapy, and to potentiate the effect of immunotherapies such as checkpoint inhibitors, both of which are evaluated in INVOKE. Tumor types for INVOKE were selected using previously presented multimodal artificial intelligence (AI) drug-matching algorithms (Grimaldi, et al., 2025). Methods: INVOKE (OKN-4395-121; NCT06789172) is a Ph1a/1b, first-in-human study of OKN4395 (oral, BID) as monotherapy (mono) or in combination with a PD1 checkpoint inhibitor (combo), in patients with advanced solid tumors. Ph1a is a Bayesian dose escalation in mono with a new parallel substudy, followed by combo dose confirmation, primarily assessing safety, establishing the Ph1b dose. Response will be assessed in updated Ph1b (cohorts of n=20): select sarcomas (mono), non-small cell lung (combo), colorectal (combo), and gastric cancer (combo). Key inclusion criteria include COX-active (Ph1a) or above-listed (Ph1b) tumors, performance status 0-1, biopsy-amenable lesions, and adequate organ function. Active CNS metastases, upper GI bleed risk factors, untreated H. pylori infection, and concomitant NSAIDs/COX inhibitors/prostaglandins are exclusionary. A new and innovative 3-period, crossover substudy in parallel with Ph1a will explore the intra-participant effects of food and gastric pH on OKN4395 pharmacokinetics. Trial data, paired pre- and on-treatment biopsies, and exploratory biomarkers will be used to enhance development using advanced agentic AI systems, including a synthetic digital twin control arm, novel methodology of which is submitted to this meeting as well. Ph1a of the study is currently recruiting in the US, UK, and Australia. Dose Level 5 concluded in December 2025 with no DLTs to that date. Clinical trial information: NCT06789172 .