Abstract P033: CC-95775, a reversible, oral bromodomain and extra-terminal (BET) inhibitor in patients with advanced solid tumors (STs): Results of a phase 1 study
Authors: Lesimple Thierry , de Miguel María José , Le Tourneau Cristophe , Ponz-Sarvise Mariano , Sablin Marie Paule , Benito Diego Salas , Hanna Bishoy , Chang Henry , Wei Xin , Garcia Marta Ocejo , Lardelli Pilar , Sánchez Tania , Palau Josep Lluís Parra , Nikolova Zariana , Calvo Emiliano 
Published: December 2021

Background: BET proteins are epigenetic readers and activators of oncogenic pathways in cancer. CC-95775 is a novel oral small molecule bromodomain inhibitor. It is a non-specific inhibitor with potent activity against all 4 BET family members (BRD2, BRD3, BRD4, BRDT), and shows additional activity towards several non-BET bromodomain proteins. Methods: CC-95775-ST-001 is a phase 1 dose-escalation study of CC-95775 in patients with advanced STs. Primary objectives were to determine safety and recommended phase 2 dose (RP2D). Secondary and exploratory objectives were pharmacokinetics (PK), pharmacodynamics (PD) and antitumor activity. Four dose levels (DLs), from 400 to 1200 mg, administered on 4 consecutive days (Day 1 to Day 4) followed by 24 days off, every four weeks (Q4W), were evaluated. Results: As of 16 Apr 2021, 24 evaluable patients were enrolled and treated. The RP2D was 1200 mg (300 mg on days 1-4 and 24 days off, Q4W). One patient treated at 800 mg and two at 1200 mg had dose-limiting toxicities: QT prolongation, left ventricular ejection fraction (LVEF) decreased and abnormal T wave. The most common treatment-related adverse event (TRAE) was thrombocytopenia in 11 patients (45.8%), 2 of them grade 3 (8.3%) and 1 grade 4 (4.2%). Safety profile consisted mainly of gastrointestinal and general disorders. Five patients (20.8%) had transient serious TRAEs: nausea, QT prolongation, abnormal T wave, posterior reversible encephalopathy syndrome and acute kidney injury. Eleven patients 11 (45.8) had disease stabilization, 9 of them with a duration of ≥ 16 weeks and 4 of them ≥ 24 weeks: melanoma, chondrosarcoma, adenoid cystic carcinoma and chordoma. Plasma exposures increased in a dose-proportional manner across DLs. Across all dose groups, median Tmax was between ~ 2-4 h post-dose, indicating rapid absorption. The terminal half-life was approximately 30 h and repeated dosing leads to drug accumulation, as expected: ~2 - 3 fold for AUC and Cmax. CC-95775 induced ≥50% decrease of the PD biomarker CCR1 at the 4-hour timepoint in the 1200 mg cohort. Conclusions: CC-95775 was well tolerated and showed preliminary antitumor activity in heavily pretreated patients with advanced malignancies. The RP2D was 1200 mg Q4W. The favorable PD profile improved tolerability and enabled less frequent dosing. Further evaluation of CC-95775 alone or in combination in STs is warranted.

Citation Format: Thierry Lesimple, María José de Miguel, Cristophe Le Tourneau, Mariano Ponz-Sarvise, Marie Paule Sablin, Diego Salas Benito, Bishoy Hanna, Henry Chang, Xin Wei, Marta Ocejo Garcia, Pilar Lardelli, Tania Sánchez, Josep Lluís Parra Palau, Zariana Nikolova, Emiliano Calvo. CC-95775, a reversible, oral bromodomain and extra-terminal (BET) inhibitor in patients with advanced solid tumors (STs): Results of a phase 1 study [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P033.