Background: The MCT inhibitor CYT-0851 blocks lactate transport resulting in glycolytic cancer cell death. Monotherapy clinical activity has been previously reported in lymphoma and solid tumors. Preclinical studies assessing CYT-0851 with chemotherapy identified enhanced growth inhibition when combined with 5-FU or gem supporting clinical evaluation. Methods: Patients (pts) with solid tumors were treated with CYT-0851 + standard dosing of cape or gem in 21- and 28-day cycles, respectively, following a 3+3 design. The primary objective was to determine the MTD. Secondary objectives included: safety, PK, and anti-tumor activity by RECIST. Results: As of Feb 1, 2023, 14 pts (pancreatic n=9; ovarian n=5) were treated in 4 cohorts (100 - 400 mg QD) with cape. No DLTs occurred, and 400 mg QD was selected as the RP2D. 8 pts (57%) experienced a treatment-related adverse event (TRAE), including 2 (14%) with a G3/4 AE. The most common related AEs were primarily G1/2 and included fatigue (21%), nausea, decreased appetite, dry skin, mucosal inflammation and maculopapular rash (all 14%). 10 pts (sarcoma n=6; HNSCC n=1; ovarian n=1; pancreatic n=2) were treated in 2 cohorts (100, 200 mg QD) with gem. No DLTs occurred. Escalation is ongoing with up to 2 further cohorts. 9 pts (90%) experienced a TRAE, including 5 (50%) with a G3/4 AE which were primarily cytopenias. The most common TRAEs were fatigue (50%), anemia (50%), neutropenia (40%), thrombocytopenia (30%), nausea, pruritus, ALT/AST increased, neutrophil decreased and WBC decreased (all 20%). CYT-0851 exposure was similar between combination therapy and monotherapy. 8 pts in the cape cohorts were response-evaluable, including 3 with ovarian cancer. 1 pt with platinum-resistant ovarian cancer had a confirmed PR with treatment ongoing at 174 days. 7 pts had SD. 6 pts in the gem cohorts were response-evaluable. 1 pt with sarcoma had a confirmed PR, 4 pts had SD and 1 had PD. Conclusions: 400 mg QD was selected as the RP2D in combination with cape as no MTD was identified. Escalation of gem + CYT-0851 is ongoing to identify the MTD. Both combinations have demonstrated an acceptable safety and tolerability profile with no unanticipated toxicities at clinically active doses. Encouraging antitumor activity has been observed in heavily pre-treated pts with both regimens including pts with ovarian cancer in the cape combo. The cape cohort is being expanded with additional pts with ovarian cancer and will be presented. Clinical trial information: NCT03997968.