We conclude that it is feasible to develop state-specific cancer incidence and survival estimates for American Indians in at least some states in different regions of the United States. Collaboration between the IHS and a state tumor registry is likely to improve the case ascertainment achieved by either agency alone.

2579 Background: Dysregulated translation of messenger RNA (mRNA) plays a role in the pathogenesis of multiple solid tumors. eFT508, a potent and highly selective small molecule inhibitor of MNK-1 and 2 blocks activation of eIF4E, a key regulator of mRNA translation, and thereby selectively regulates translation of a small set of mRNAs. In addition to direct antitumor activity, eFT508 triggers an anti- tumor immune response and enhances responses to checkpoint inhibitors in preclinical models. Methods: Using a 3+3 dose escalation schema, cohorts of solid tumor patients (pts) were treated with eFT508 administered orally once daily at doses ranging from 50 mg to 600 mg. Results: 28 pts were treated, and the most common tumor types were colorectal cancer (8), prostate cancer (3), and soft tissue sarcoma (3). Median number of prior therapies was 4. The most common observed adverse events (AEs) included nausea (47%), vomiting (47%), dyspepsia (23%), fatigue (20%), and constipation (20%). Two pts treated at 600 mg experienced Gr 3 related AEs, including one pt with Gr3 nausea and vomiting (met criteria for dose limiting toxicity) and one pt with reversible Gr3 AST/ALT elevation. 6 pts achieved stable disease with duration ranging from 82 to 196 days. Pharmacokinetic analysis revealed that eFT508 is bioavailable and rapidly absorbed, with median Tmax of 2 hours and a mean T1/2 of 12 hours. Minimal accumulation was observed between Days 1 and 14/15, with mean accumulation factor of 1.2-fold. Analysis of eIF4E phosphorylation in peripheral blood cells suggested that doses ≥ 300 mg achieved engagement sufficient for maximal efficacy as predicted by preclinical models. Conclusions: Preliminary results suggest that eFT508 is well tolerated, and dose escalation continues with a cohort of pts providing pretreatment and on treatment biopsies for evaluation of target engagement and immunomodulatory effects. After determination of the recommended phase 2 dose, further evaluation will include monotherapy cohorts in specific tumor types as well as cohorts to evaluate efficacy and tolerability in combination with checkpoint inhibitors. Clinical trial information: NCT02605083.

e14145 Background: Dysregulated translation of messenger RNA (mRNA) plays a role in the pathogenesis of solid tumors. Tomivosertib (T), a potent and highly selective small molecule inhibitor of MNK-1 and 2 blocks activation of eIF4E, a key regulator of mRNA translation, selectively regulating translation of a set of mRNAs. Preclinically, T triggers an anti-tumor immune response and enhances responses to checkpoint inhibitors. Avelumab is a fully human checkpoint inhibitor antibody directed against PD-L1. Methods: Part 1: In a 3+3 dose escalation patients (pts) with MSS CRC failing ≥2 prior therapies for metastatic disease received escalating doses of T, administered orally bid, with a fixed dose of 10 mg/kg avelumab q2w. Part 2: Pts were randomized (2:1) to combination therapy at the recommended phase 2 dose (RP2D) from part 1 or T alone. Primary endpoint is objective response rate. All pts have a pretreatment and on treatment biopsy to evaluate target engagement, tumor infiltrating lymphocytes and biomarkers of immune activation. Results: The RP2D for the combination was 200 mg bid T (single agent RP2D) with 10mg/kg avelumab q2w. At this dose level, 1 of 7 pts experienced a dose limiting toxicity being unable to complete the first 28 day cycle due to low grade (1/2) toxicities (nausea, fatigue, myalgia). In part 2, 30 pts were randomized to combination and 15 to monotherapy (25 male, 20 female: mean age 53.9 years, range 32-80 years). The most common adverse events, irrespective of causality were grade 1/2 gastrointestinal (including nausea, vomiting, abdominal pain, constipation and diarrhea) occurring in 77% (n = 23) of the combination and 67% (n = 10) of the monotherapy arm. Toxicities occurring more frequently in the combination arm included diarrhea, constipation, fatigue, myalgia/arthralgia, hypercalcemia and skin rash. Efficacy evaluation is pending from part 2. One pt with confirmed MSS status in part 1 treated at the RP2D achieved a confirmed Partial Response of greater than 8 months. Conclusions: Preliminary data suggest that the combination of T and avelumab has an acceptable safety profile with robust target engagement and demonstrated initial signs of activity. Updated efficacy and biological biopsy data will be presented at the conference. Clinical trial information: NCT03258398.

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