A phase I/II study combining tosedostat with capecitabine in patients with metastatic pancreatic ductal adenocarcinoma (PDAC)

410 Background: Recent advances in front-line therapy have improved survival in patients with advanced PDAC. A fluorouracil-based regimen is recommended for patients who progress on a gemcitabine-based therapy. Tosedostat is an oral aminopeptidase inhibitor that disrupts the cleavage of amino acids from peptides downstream of proteasomal degradation. It prevents the recycling of free amino acids, leads to intracellular depletion of amino acids, and triggers an amino acid deprivation response that subsequently results in apoptosis. Because PDAC cells frequently upregulate expression of these aminopeptidases, tosedostat offers therapeutic promise, particularly in combination with fluoropyrimidines. Methods: This is a single institution phase I/II trial to evaluate the safety and toxicity of tosedostat plus capecitabine in patients with metastatic PDAC progressed on a gemcitabine-based therapy. The phase I portion is being conducted in a dose de-escalation fashion, with two dose levels of tosedostat (120 mg or 60 mg) p.o. daily on days 1 to 21 with capecitabine 1000 mg/m2 p.o. BID on days 1 to 14 of a 21-day cycle. If more than one out of 6 patients in the tosedostat (120 mg) cohort experience a dose limiting toxicity (DLT), then 6 more will be enrolled to the tosedostat (60 mg) cohort. The primary objective of the phase I portion is to determine the optimal phase II dose. The primary objective of the phase II portion is to determine the progression-free survival at 3 months. Secondary objectives include the overall response rate, overall survival and CA 19-9 response. To avoid futility, interim analysis is planned after 10 evaluable patients enrolled. Results: Up to date, a total of 11 patients have been enrolled in the study, and 10 patients are evaluable. No DLT have been observed. Tosedostat at a dose of 120 mg with capecitabine is extremely well tolerated. Prolonged stable disease has been observed in 4 (40%) patients with a time on treatment of 10 months, 7.5 months, 5.5 months and 4 months, and 3 of the 4 patients remain on the trial. Conclusions: The combination of tosedostat and capecitabine is a well-tolerated regimen with impressive clinical activity in the subset of patients studied thus far. Clinical trial information: NCT02352831.