A phase I study of olaparib in combination with capecitabine-based chemoradiation (CRT) in patients (pts) with locally advanced pancreatic cancer (LAPC).

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709 Background: Olaparib is a potent inhibitor of PARP-1, which has a critical role in signalling DNA single strand breaks (SSB) as part of the base excision repair pathway, and may have radio-sensitizing effects due to impaired resolution of radiation induced SSB. We hypothesize that O may potentiate the effects of X-CRT in pts with LAPC. Methods: Eligible pts with LAPC, ECOG < 1, tumor diameter < 6cm, with stable disease (SD) or response after 12 weeks’ induction chemotherapy, were treated with 1 of 4 escalating doses of O given bid po starting on day -3, and then in combination with X (830 mg/m2 bid) and radiation (50·4 Gy in 28 fractions) all administered Mon-Fri. Dose limiting toxicities (DLT) were determined on clinical and lab toxicity assessments (NCI-CTC AE v4.03) performed weekly from the start of O until completion of O plus X-CRT (i.e. 6 weeks). Dose escalation continued with a rolling-six design until the Maximum Tolerated Dose (MTD) was reached. Blood samples for PK analyses of O and PD measurement (inhibition of PARP activity) were collected on day -3 (O monotherapy) and during week 1 of O + X-CRT. Results: 18 pts, (9 m, 9 f, ECOG 0/1 [n=6/12]), age range 49-81 (median=70) years, with histologic (14) or cytologic (4) proven LAPC, had received induction chemotherapy with gemcitabine [GEM] (n=2), GEM + X (12), or FOLFIRINOX (3) with partial response (n=4) or stable disease (14). Pts received 50 (3), 100 (4), 150 (6), or 200 (5) mgs bid of O with X+CRT. DLTs were observed in 2 pts (both at 200mgs bid): 1 pt with grade 3 nausea (on optimal anti-emetics) and grade 3 fatigue, 1 pt with grade 3 anorexia. 6 pts were subsequently recruited at 150mgs bid with no DLTs. No pts had complete response, 2 pts had partial response (1 pt each at 100 and 150 mgs bid) and 1 pt (at 100 mgs bid) had progressive disease; the remaining 14 pts had SD. Conclusions: The recommended dose (RP2) of O is 150mgs bid when given in combination with X + CRT in LAPC. Recruitment of up to 12 pts with borderline operable LAPC at the RP2 is ongoing. PK analyses of O, PD studies (PARP inhibition – PBMCs; cytokeratin 18 – serum; γH2AX foci – hair follicles), and exploratory predictive marker studies (tumor – NGS; RNA exome sequencing) are ongoing. Clinical trial information: ISRCTN10361292.

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