547P - Rucaparib + sacituzumab govitecan (SG): Initial data from the phase Ib/II SEASTAR study (NCT03992131)

Background

Preclinically, PARP inhibitors (PARPi) + TOP1 inhibitors have shown highly synergistic antitumour effects, but clinical development has been hampered by overlapping toxicities. Tumour-targeted delivery of a TOP1 inhibitor may reduce systemic toxicity of the combination; thus, we evaluated the PARPi rucaparib + SG, an antibody-drug conjugate composed of an anti-Trop2 antibody coupled to the active metabolite of irinotecan (SN-38) via a unique hydrolyzable linker.

Methods

For phase Ib, eligible patients (pts) had metastatic triple-negative breast cancer (TNBC); urothelial cancer (UC); platinum-resistant ovarian cancer (OC); or solid tumour with deleterious mutation in a homologous recombination repair (HRR) gene (BRCA1/2, PALB2, or RAD51C/D). Prior PARPi was allowed. A 3+3 design was used; starting dose was rucaparib 300 mg PO BID + SG 6 mg/kg IV on days 1 and 8 of a 21-day cycle in cohort 1; rucaparib dose was reduced to 300 mg QD in cohort 2. DLTs were assessed during cycle (C) 1. Growth factor (GF) support was allowed except during the DLT period.

Results

In cohort 1, grade (G) 4 neutropenia during C1 was dose limiting (n/N=2/3). In cohort 2, G3/4 neutropenia led to treatment delay of C2 in 3/3 pts. Despite early toxicities, all 6 pts continued treatment (range, 12–27+ weeks), with side effects effectively managed with dose modification and/or GF support. Three pts had a confirmed PR, including 2 pts previously treated with niraparib until PD; 2 responders did not have HRR gene mutations.

Conclusions

Initial encouraging signs of antitumour activity were seen with rucaparib + SG in pts with advanced solid tumours, including pts with prior PARPi exposure. Continuous treatment is feasible with dose modification and/or GF support. Further evaluation is warranted. Table: 547P

+, ongoing; ND, none detected.

Clinical trial identification

NCT03992131.

Editorial acknowledgement

Editorial support funded by Clovis Oncology was provided by Frederique H. Evans, MBS, of Ashfield Healthcare Communications.

Legal entity responsible for the study

Clovis Oncology, Inc.

Funding

Clovis Oncology, Inc.

Disclosure

T.A. Yap: Advisory/Consultancy, Research grant/Funding (institution): Clovis Oncology ; Advisory/Consultancy, Research grant/Funding (institution): AstraZeneca; Advisory/Consultancy, Research grant/Funding (institution): Bayer; Research grant/Funding (institution): Constellation; Research grant/Funding (institution): Cyteir; Research grant/Funding (institution): Eli Lilly; Advisory/Consultancy, Research grant/Funding (institution): EMD Serono; Research grant/Funding (institution): Forbius/Formation Biologics; Advisory/Consultancy, Research grant/Funding (institution): F-Star; Research grant/Funding (institution): GlaxoSmithKline; Research grant/Funding (institution): Genentech; Research grant/Funding (institution): ImmuneSensor; Research grant/Funding (institution): Ipsen; Research grant/Funding (institution): Jounce; Research grant/Funding (institution): Karyopharm; Research grant/Funding (institution): Kyowa; Research grant/Funding (institution): Novartis; Advisory/Consultancy, Research grant/Funding (institution): Pfizer; Research grant/Funding (institution): Ribon Therapeutics; Research grant/Funding (institution): Regeneron; Research grant/Funding (institution): Sanofi; Advisory/Consultancy, Research grant/Funding (institution): Seattle Genetics; Research grant/Funding (institution): Tesaro; Research grant/Funding (institution): Vertex Pharmaceuticals; Advisory/Consultancy: Almac; Advisory/Consultancy: Aduro; Advisory/Consultancy: Atrin; Advisory/Consultancy: Axiom; Advisory/Consultancy: Calithera; Advisory/Consultancy: Cybrexa; Advisory/Consultancy: Guidepoint; Advisory/Consultancy: Ignyta; Advisory/Consultancy: I-Mab; Advisory/Consultancy: Jansen; Advisory/Consultancy: Kyn Therapeutics; Advisory/Consultancy: Merck; Advisory/Consultancy: Roche; Advisory/Consultancy: Zai Labs. E.P. Hamilton: Honoraria (institution), Research grant/Funding (institution): Pfizer; Honoraria (institution), Research grant/Funding (institution): Genentech/Roche; Honoraria (institution), Research grant/Funding (institution): Lilly; Honoraria (institution), Research grant/Funding (institution): Puma Biotechnology; Honoraria (institution), Research grant/Funding (institution): Daiichi Sankyo; Honoraria (institution), Research grant/Funding (institution): Mersana Therapeutics; Honoraria (institution), Research grant/Funding (institution): Boehringer Ingelheim; Honoraria (institution), Research grant/Funding (institution): AstraZeneca; Honoraria (institution), Research grant/Funding (institution): Novartis; Honoraria (institution), Research grant/Funding (institution): Silverback Therapeutics; Honoraria (institution), Research grant/Funding (institution): Black Diamond; Honoraria (institution): NanoString; Research grant/Funding (institution): Seattle Genetics; Research grant/Funding (institution): Hutchinson MediPharma; Research grant/Funding (institution): OncoMed; Research grant/Funding (institution): MedImmune; Research grant/Funding (institution): StemCentrx; Research grant/Funding (institution): Curis; Research grant/Funding (institution): Verastem; Research grant/Funding (institution): Zymeworks; Research grant/Funding (institution): Syndax; Research grant/Funding (institution): Lycera; Research grant/Funding (institution): Rgenix; Research grant/Funding (institution): Millenium; Research grant/Funding (institution): TapImmune; Research grant/Funding (institution): BerGenBio; Research grant/Funding (institution): Medivation; Research grant/Funding (institution): Tesaro; Research grant/Funding (institution): Eisai; Research grant/Funding (institution): H3 Biomedicine; Research grant/Funding (institution): Radius Health; Research grant/Funding (institution): Acerta; Research grant/Funding (institution): Takeda; Research grant/Funding (institution): Macrogenics; Research grant/Funding (institution): AbbVie; Research grant/Funding (institution): Immunomedics; Research grant/Funding (institution): FujiFilm; Research grant/Funding (institution): Effector; Research grant/Funding (institution): Merus;Research grant/Funding (institution): NuCana; Research grant/Funding (institution): Regeneron;Research grant/Funding (institution): Leap Therapeutics; Research grant/Funding (institution): Taiho Pharmaceutical; Research grant/Funding (institution): EMD Serono; Research grant/Funding (institution): ArQule; Research grant/Funding (institution): Syros; Research grant/Funding (institution): Clovis; Research grant/Funding (institution): Cytomx; Research grant/Funding (institution): InventisBio; Research grant/Funding (institution): Deciphera;Research grant/Funding (institution): Unum Therapeutics; Research grant/Funding (institution): Sermonix Pharmaceuticals; Research grant/Funding (institution): Sutro; Research grant/Funding (institution): Aravive; Research grant/Funding (institution): Zenith Epigenetics; Research grant/Funding (institution): Arvinas; Research grant/Funding (institution): Torque; Research grant/Funding (institution): Harpoon; Research grant/Funding (institution): Fochon; Research grant/Funding (institution): Orinove; Research grant/Funding (institution): Molecular Templates; Research grant/Funding (institution): Compugen; Research grant/Funding (institution): G1Therapeutics; Research grant/Funding (institution): Karyopharm Therapeutics; Research grant/Funding (institution): Torque Therapeutics. T.M. Bauer: Advisory/Consultancy: Blueprint Medicines; Advisory/Consultancy: Exelixis; Advisory/Consultancy: Foundation Medicine; Advisory/Consultancy: Gaurdant Health; Advisory/Consultancy: Loxo; Advisory/Consultancy, Travel/Accommodation/Expenses: Pfizer; Speaker Bureau/Expert testimony: Bayer; Travel/Accommodation/Expenses: Clovis Oncology; Travel/Accommodation/Expenses: Astellas Pharma; Travel/Accommodation/Expenses: AstraZeneca; Travel/Accommodation/Expenses: EMD Serono; Travel/Accommodation/Expenses: Genetech; Travel/Accommodation/Expenses: Lilly; Travel/Accommodation/Expenses: Merck; Travel/Accommodation/Expenses: Novartis; Travel/Accommodation/Expenses: Pharmacyclics; Travel/Accommodation/Expenses: Sysmex. R. Jeselsohn: Research grant/Funding (self): Lilly; Research grant/Funding (self): Pfizer; Advisory/Consultancy: Carrick ; Advisory/Consultancy: Luminex. A. Enke: Shareholder/Stockholder/Stock options, Full/Part-time employment: Clovis Oncology. S. Hurley: Shareholder/Stockholder/Stock options, Full/Part-time employment: Clovis Oncology. K.K. Lin: Shareholder/Stockholder/Stock options, Full/Part-time employment: Clovis Oncology. K. Wride: Shareholder/Stockholder/Stock options, Full/Part-time employment: Clovis Oncology. H. Giordano: Shareholder/Stockholder/Stock options, Full/Part-time employment: Clovis Oncology. G. Shapiro: Advisory/Consultancy, Research grant/Funding (self): Eli Lilly; Advisory/Consultancy, Research grant/Funding (self): Merck KGaA/EMD-Serono; Research grant/Funding (self): Merck; Advisory/Consultancy, Research grant/Funding (self): Sierra Oncology; Advisory/Consultancy: Pfizer; Advisory/Consultancy: G1 Therapeutics; Advisory/Consultancy: Roche; Advisory/Consultancy: Bicycle Therapeutics; Advisory/Consultancy: Fusion Pharmaceuticals; Advisory/Consultancy: Cybrexa Therapeutics; Advisory/Consultancy: Astex; Advisory/Consultancy: Almac; Advisory/Consultancy: Ipsen; Advisory/Consultancy: Bayer; Advisory/Consultancy: Angiex; Advisory/Consultancy: Daiichi Sankyo; Advisory/Consultancy: Seattle Genetics; Advisory/Consultancy: Boehringer Ingelheim; Advisory/Consultancy: ImmunoMet; Advisory/Consultancy: Asana; Advisory/Consultancy: Artios; Advisory/Consultancy: Atrin ; Advisory/Consultancy: Concarlo Holdings; Licensing/Royalties, patent: Cyclacel Pharmaceuticals. All other authors have declared no conflicts of interest.