Table 1.

Phase I study 201973: primary and secondary objectives and endpoints.

Objectives	Endpoints
Primary
To determine a RP2D of molibresib, when given in combination with fulvestrant, in women with advanced or metastatic HR+/HER2− breast cancer	Safety profile (e.g., AE, SAE, DLT, dose reductions, or delays), ORR, defined as CR rate plus PR rate, PK data
Secondary
To determine the safety, tolerability, and MTD of molibresib, when given in combination with fulvestrant, in women with advanced or metastatic HR+/HER2− breast cancer To evaluate the clinical activity of molibresib and fulvestrant, when given in combination, in women with advanced or metastatic HR+/HER2− breast cancer To characterize the exposure to molibresib and fulvestrant, when given in combination	AE, SAE, dose reductions or delays, withdrawals due to toxicities, and changes in safety assessments (e.g., laboratory parameters, vital signs, ECG, cardiotoxicity, gastrointestinal, etc.) DCR (defined as CR plus PR plus SD rate ≥6 mo), duration of response, and PFS Concentrations of molibresib, molibresib-relevant metabolites, and fulvestrant following administration in combination

Abbreviations: AE, adverse event; CR, complete response; DCR, disease control rate; DLT, dose-limiting toxicity; ECG, electrocardiogram; HR⁺/HER2⁻, hormone receptor-positive/human epidermal growth factor receptor 2-negative; MTD, maximum tolerated dose; ORR, objective response rate; PFS, progression-free survival; PK, pharmacokinetic; PR, partial response; RP2D, recommended phase II dose; SAE; serious adverse event; SD, stable disease.