Background: Platinum and PARP inhibitors have both shown activity in BRCA-associated breast cancer (BC) patients (pts). We have conducted a phase I trial of carboplatin (Carb) and velapirib [V], a PARP inhibitor, to define dose limiting toxicities [(DLT) during cycle (C) 1] and the maximum tolerated dose (MTD). Methods: BRCA 1 or 2 carriers with stage IV BC were eligible. Carb starting at an AUC of 6 was given IV every 21 days (length of planned C) and V was administered orally, BID at dose levels (L) L1 through L5 (highest L planned). Results: 22 pts (21 eligible/evaluable, 20 with measurable BC) carrying BRCA1 (10) or BRCA2 (11), or both (1) mutations were accrued. Median age: 45 years, (32-65); 68% of BCs were ER+, and 10% were HER2+. In the table below are the schema, incidence of DLTs, and # of Cs on study. Toxicities: At L1, grade ¾ DLTs with C 1 were seen in 2/6 evaluable pts (1 pt w/grade 3 hyponatremia, pleural effusion, and dehydration, and 1pt w/grade 4 thrombocytopenia [PLT]), leading to deescalation of carb (AUC 5) for pts treated at Ls 2-5. At L2, 1 of 6 pts had grade 4 PLT. There were no DLTs at Ls 3 and L4. L5 is currently being expanded to 6 pts (3 currently enrolled, 1 pt with grade 4 granulocytopenia (Gr) and grade PLT reached DLT). Non-DLT dose delays mostly due ≥ grade 2 Gr or PLT were needed at 60%, 53%, 53%, and 43% of Cs in pts treated on Ls 1-4. Response: In 12 eligible pts treated at Ls 1 and 2, 2 complete and 6 partial responders (67%) and a clinical benefit (CB) of 75% were seen. All pts at Ls 3-5 are still being treated, and in pts treated at Ls 3 and 4, 2 unconfirmed PRs, and 4 cases of stable disease were seen, with L5 too early to assess. Conclusions: The combination of Carb at an AUC of 5 and daily V at doses 150 to 200 mg BID is feasible and the MTD is being defined. In preliminary analysis, response and CB rates are better than expected with the individual agents alone, providing justification to proceed with a planned phase II randomized single agent versus combination trial.

Dose levels	L1	L2	L3	L4	L5 (highest planned L)
Carb AUC	6	5	5	5	5
V in mg	50 BID	50 BID	100 BID	150 BID	200 BID
# of pts	7 (1 ineligible)	6	3	3	3 (and 3 in screening)
Evaluable pts	6	6	3	3	3
DLTs	2	1	0	0	1
# of Cs given	9 (1-15)	8.5+ (1-11)	6+ (6+)	3+ (3+ to 4+)	1+ (1+ to 2+)