Background: RX-3117 is an oral small-molecule antimetabolite, cyclopentyl pyrimidyl nucleoside that is activated by uridine cytidine kinase 2. RX-3117 has shown efficacy in xenograft models of gemcitabine resistant pancreatic, bladder and colorectal cancer. Data from stage 2 of the Phase 1b/2a clinical study of RX3117 as a single agent in subjects with metastatic pancreatic cancer is described below. Methods: Stage 2 of the Phase 1b/2a study (NCT02030067) is designed to evaluate safety, tolerability and efficacy following treatment with 700 mg administered orally once-daily for 5 consecutive days with 2 days off per week for 3 weeks with 1 week off in each 4 week cycle. Eligible subjects (aged ≥ 18 years) had relapsed/refractory metastatic pancreatic cancer. The primary endpoint is a ≥ 20% rate of progression free survival (PFS) benefit (i.e., proportion of subjects with stable disease for at least 4 months) and/or a 10% of evaluable subjects with a partial response rate or better. Results: As of Sep 2017, 44 subjects have been enrolled (22 females, 22 males). The median age was 68 years, ECOG performance statuses were 0 (13 subjects) and 1 (31 subjects) and 6 subjects had received 4 or more prior therapies. One subject had an unconfirmed partial response and 21 subjects met the primary endpoint of stable disease with a duration of 30-224 days. The most frequent adverse events were mild to moderate anemia (19%), mild to moderate fatigue (15%), mild to moderate diarrhea (11%), and severe anemia (9%). Conclusions: This ongoing trial shows an early efficacy signal where RX-3117 is active against advanced pancreatic cancer. The study continues to enroll subjects with advanced pancreatic cancer into stage 2. A phase 2 study with nab-paclitaxel in first-line patients with advanced pancreatic cancer has been started. Clinical trial information: NCT02030067