An Open Label, Escalating Multiple Dose Study to Evaluate the Safety, Toxicity, and Pharmacokinetics of BTX A51 Alone and in Combination With Fulvestrant in Subjects With Advanced Solid Tumors and Estrogen Receptor Positive, Human Epidermal Growth Factor Receptor 2 Negative Metastatic Breast Cancer

Summary

This is a multicenter, open label, nonrandomized, sequential dose escalation/dose ranging, multiple dose study designed to evaluate the safety, toxicity, and PK as well as preliminary efficacy of BTX-A51 alone and in combination with fulvestrant in subjects with advanced solid tumors. The study will be done in three phases, described below. Phase 1a (Dose Escalation Phase): The Phase 1a portion is designed to determine the dose limiting toxicities (DLTs), maximum tolerated dose (MTD), and recommended Phase 2 dose (RP2D) of orally administered BTX-A51. BTX-A51 will be administered once daily on a weekly schedule of 5 days on/2 days off. Dose escalation will proceed according to a modified 3+3 design. Each cycle will consist of 28 days (4 weeks), and the DLT observation period will be the first cycle (i.e., 28 days after initiation of dosing). A DLT may be observed in no more than 0 out of 3 or 1 out of 6 subjects who have completed the DLT observation period before the next cohort initiates accrual. Barring DLT, sequential dose escalation of BTX-A51 is planned with up to a total of 6 dose levels; on the basis of these an MTD will be identified. The MTD is defined as the highest dose level with a subject incidence of DLTs of 0 or 1 out of 6 during the first 28 days of study drug dosing. A minimum of 6 subjects needs to be treated at a dose level before this dose level can be deemed as the MTD. Phase 1b (Monotherapy Dose Ranging Phase): Dose expansion may begin when the RP2D has been determined. Up to 40 additional subjects at each of the 2 dose levels will be enrolled to evaluate safety and preliminary efficacy of BTX-A51 in subjects with estrogen receptor positive (ER+), human epidermal growth factor receptor 2 negative (HER2-), GATA3 mutant (mt) and wild-type (wt) metastatic breast cancer (mBC). Dosing in this phase of the study consists of the first cycle of therapy (i.e., 28 days). Phase 1c (Combination Safety Phase): The Phase 1c portion will evaluate the safety and tolerability of orally administered BTX-A51 at two dose levels combined with fulvestrant. The first combo cohort may be initiated after DEC review of the 6 subject lead-in phase of the high dose monotherapy cohort in Phase 1b. Dose escalation will proceed according to a 3+3 design. Each cycle will consist of 28 days (4 weeks), and the DLT observation period will be the first cycle (i.e., 28 days after initiation of dosing).

Eligibility

Age range

18+ years

Sex

All

Healthy volunteers

No

Interventions

• Drug
  BTX-A51

  One 28 day cycle of treatment will consist of 4 weeks of treatment with a weekly dosing schedule of up to 5 days per weekf.

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