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A Trial of BXCL701 and Pembrolizumab in Patients With mCRPC Either Small Cell Neuroendocrine Prostate Cancer or Adenocarcinoma Phenotype.

Phase 1b/2 Study of BXCL701, a Small Molecule Inhibitor of Dipeptidyl Peptidases, Administered in Combination With the Anti-Programmed Cell Death 1 Monoclonal Antibody Pembrolizumab in Patients With mCRPC Either Small Cell Neuroendocrine Prostate Cancer or Adenocarcinoma Phenotype

Status
Completed
Phases
Phase 1Phase 2
Study type
Interventional
Source
ClinicalTrials.gov
Registry ID
NCT03910660
Enrollment
98
Registered
2019-04-10
Start date
2019-02-12
Completion date
2025-08-31
Last updated
2026-05-15

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

Neuroendocrine Tumors, Prostate Cancer, Small Cell Carcinoma

Brief summary

An open-label, multicenter, Phase 1b/2 study to identify the recommended Phase 2 dose and assess the efficacy and safety of BXCL701 administered orally, as monotherapy and in combination with PEMBRO, in patients with mCRPC. Patients enrolled in the Phase 2a portion of the study will have either Small Cell Neuroendocrine Prostate Cancer(SCNC)(Cohort A) or adenocarcinoma phenotype (Cohort B), while the Phase 2b randomized portion of the study will enroll only the histologic subtype(s) showing preliminary evidence in Phase 2a. The study will also assess other efficacy parameters, such as rPFS, PSA PFS, OS, and DOR, as well as the safety of the combined treatment. The study will consist of three components.

Detailed description

An open-label, multicenter, Phase 1b/2 study to identify the recommended Phase 2 dose and assess the efficacy and safety of BXCL701 administered orally, as monotherapy and in combination with PEMBRO, in patients with mCRPC. Patients enrolled in the Phase 2a portion of the study will have either Small Cell Neuroendocrine Prostate Cancer(SCNC)(Cohort A) or adenocarcinoma phenotype (Cohort B), while the Phase 2b randomized portion of the study will enroll only the histologic subtype(s) showing preliminary evidence in Phase 2a. The study will also assess other efficacy parameters, such as rPFS, PSA PFS, OS, and DOR, as well as the safety of the combined treatment. The study will consist of three components. 1. Phase 1b: Safety and tolerability of the combination of BXCL701 administered once daily (QD) on Days 1 to 14 of a 21-day cycle plus PEMBRO 200 mg administered intravenously (IV) on Day 1 of every 21 days will be assessed and confirmed in patients with mCRPC. In the first cohort enrolled in the study, the initial dose level of BXCL701 will be 0.4 mg; if there are no safety concerns, this will be escalated to a total daily dose of 0.6 mg. 2. Phase 2a (Simon 2 Stage): Patients will be treated with BXCL701 in combination with PEMBRO. Patients will be grouped in 1 of 2 cohorts based on phenotype. * Cohort A: Patients with any Small Cell/Neuroendocrine features, either de novo or treatment-emergent included mixed SCNC. * Cohort B: Cohort B: Patients with adenocarcinoma and no evidence of small cell or neuroendocrine features. Phase 2b (for the histologic subtype\[s\] showing preliminary efficacy in Phase 2a): Patients within a given subtype will be randomized 2:1 to receive either BXCL701 combined with PEMBRO or BXCL701 monotherapy. Phase 1b: Patients will be observed for dose-limiting toxicity (DLT) during Cycle 1. Three patients will be treated initially with BXCL701 0.4 mg plus PEMBRO: * If there are no DLTs in Cycle 1, the dose of BXCL701 will be escalated to a total daily dose of 0.6 mg in the next cohort of 3 patients. * If ≥1 of the 3 original patients has a DLT in Cycle 1, after a discussion between the sponsor and the investigator, either 3 patients (if 1 patient experiences a DLT) or 6 to 9 patients (if 2 or 3 patients experiences a DLT) will be added at the 0.4 mg BXCL701 dose level. For this expanded 0.4 mg cohort: * If none of the patients experience a DLT, consideration will be given to dose escalation to BXCL701 0.6 mg plus PEMBRO * If 1/3 of the patients experience a DLT, the Phase 2 can commence * If \>1/3 of the patients experience a DLT, a discussion will be held between the investigators and sponsors as to how to proceed. Following dose escalation to BXCL701 0.6 mg plus PEMBRO in 3 patients: * If there are no DLTs at this dose level, the Phase 2a can commence. * If ≥1/3 patients have a DLT in Cycle 1, after a discussion between the sponsor and the investigator, 6 to 9 patients will be added at the 0.6 mg BXCL701 total daily dose level; and consideration of an alternate dosing (e.g., split dose) schedule may be given. * For this additional cohort of 6 to 9 patients: * If \</= 1/3 of the patients experience a DLT, the Phase2a can commence. * If \>1/3 of the patients experience a DLT, consideration will be given to the use of a 0.4 mg total daily dose of BXCL701, or an intermediate dose, plus PEMBRO in the Phase 2a.

Interventions

DRUGBXCL701 plus Pembrolizumab

BXCL701 tablets dosage strengths include 0.05mg and 1mg tablets for oral administration. BXCL701 will be administered orally as 0.05mg and 1mg tablets. Patients will take the prescribed number of tablets on Days 1 to 14 of each cycle, for a total daily dose of 0.4 mg, 0.6 mg, or an intermediate dose. BXCL701 will be continued until PD or unacceptable toxicity, or closure of the study by the sponsor; no maximum duration of therapy has been set. BXCL701 should not be taken on an empty stomach. On days when PD studies are being performed, BXCL701 should be administered at the study center and should be administered at approx. the same time of day on each treatment day in the cycle. In cycles in which PD are not evaluated, BXCL701 also should be administered at approx. the same time of day on each treatment day. The PEMBRO dose will be 200 mg, administered as an IV infusion over 30 mins. on Day 1 of each 21-day cycle.

DRUGBXCL701 monotherapy

BXCL701 tablets dosage strengths include 0.05mg and 1mg tablets for oral administration. BXCL701 will be administered orally as 0.05mg and 1mg tablets. Patients will take the prescribed number of tablets on Days 1 to 14 of each cycle, for a total daily dose of 0.4 mg, 0.6 mg, or an intermediate dose. BXCL701 will be continued until PD or unacceptable toxicity, or closure of the study by the sponsor; no maximum duration of therapy has been set. BXCL701 should not be taken on an empty stomach. On days when PD studies are being performed, BXCL701 should be administered at the study center and should be administered at approx. the same time of day on each treatment day in the cycle. In cycles in which PD are not evaluated, BXCL701 also should be administered at approx. the same time of day on each treatment day.

Sponsors

BioXcel Therapeutics Inc
Lead SponsorINDUSTRY

Study design

Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
TREATMENT
Masking
NONE

Eligibility

Sex/Gender
MALE
Age
18 Years to No maximum
Healthy volunteers
No

Inclusion criteria

All patients must satisfy the following inclusion and

Exclusion criteria

to be eligible for entry into the trial. 1. Patient has evidence of progressive, metastatic castration-resistant disease, as defined by PCWG3 criteria. a. Patients with de novo small cell prostate cancer are not required to have received androgen deprivation therapy (ADT). 2. Progression during or following completion of at least 1 prior line of systemic therapy for locally advanced or metastatic prostate cancer. 3. Phases 2a and 2b Only: SCNC - Cohort A of Phase 2a only: 1. Patient has histologic evidence of SCNC either with archival tissue or a fresh tumor biopsy obtained during screening. Tumor biopsy tissue must be submitted for a central laboratory pathology review; however, enrollment can proceed if SCNC is determined by a local pathology review. 2. Patient has previously received at least 1 prior line of cytotoxic chemotherapy. Patients who either have refused chemotherapy or are considered unsuitable for chemotherapy may be eligible following discussion with the sponsor. 3. Must be willing to undergo metastatic tumor biopsy during Screening. Requirement may be waived in patients without safely accessible lesion or for patients with evaluable archival metastatic tumor tissue 4. Has measurable disease per RECIST 1.1 criteria. Adenocarcinoma - Cohort B of Phase 2a; randomized population for Phase 2b 1. Patient has histologically or cytologically confirmed adenocarcinoma of the prostate without small cell neuroendocrine features. 2. Patients with soft tissue disease must provide a fresh core or excisional biopsy or archival tissue from a site not previously irradiated for central pathology review; however enrollment may proceed if predominant adenocarcinoma without small cell neuroendocrine features is determined by local pathology review. 3. Has been treated with at least 1 but no more than 2 second generation AR pathway target agents (e.g., abiraterone acetate and/or enzalutamide or other next generation agent) and at least 1 regimen/line of taxane containing chemotherapy in the mCSPC or mCRPC setting. Patients with known actionable mutations should have progressed on applicable standard care targeted therapy or have documented intolerance to or be unsuitable for such therapy. 4. RECIST 1.1 measurable disease or detectable bone metastases by whole body bone scintigraphy. 4. Patient has serum testosterone \<50 ng/dL during Screening except for those with de novo small cell prostate cancer. a. Patients with treatment-emergent SCNC without a history of bilateral orchiectomy are required to remain on luteinizing hormone-releasing hormone (LHRH) analog during the course of protocol therapy except for patients with de novo small cell prostate cancer. 5. Patient has Eastern Cooperative Oncology Group (ECOG) performance status of 0-2. 6. Patient is ≥18 years of age. 7. Patient's acute toxic effects of previous anticancer therapy have resolved to ≤Grade 1 except for Grade 2-3 peripheral neuropathy or any grade of alopecia. 8. Patient has adequate baseline organ function, as demonstrated by the following: 1. Serum creatinine ≤1.5 times institutional upper limit of normal (ULN) or calculated creatinine clearance \>50 mL/min; 2. Serum albumin ≥2.5 g/dL; 3. Total bilirubin ≤1.5 × ULN; 4. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤2.5 × institutional ULN (patients with hepatic metastases must have AST/ALT ≤5 × ULN). 9. Patient has adequate baseline hematologic function, as demonstrated by the following: 1. Absolute neutrophil count (ANC) ≥1.5 × 109/L. 2. Hemoglobin ≥8 g/dL and no red blood cell transfusions during the prior 14 days. 3. Platelet count ≥100 × 109/L and no platelet transfusions during the prior 14 days. 10. Male patients and their female partners of childbearing potential must agree and commit to use a barrier contraception throughout the duration of the study until at least 6 months following the last dose of study drug, in addition to their female partners using either an intrauterine device or hormonal contraception and continuing until at least 6 months following the last dose of study drug. This criterion may be waived for male patients who have had a vasectomy \>6 months before signing the informed consent form. Exception: In the United States, female partners of study participants are not required to use contraception as a condition of their partners' eligibility, but female partners with child bearing potential should consider use of effect methods of contraception for the duration of their male partners' study participation and for at least 6 months following the last dose of study medication. 11. Patient has signed informed consent prior to initiation of any study-specific procedures or treatment. 12. Patient is able to adhere to the study visit schedule and other protocol requirements, including follow-up for overall survival (OS).

Design outcomes

Primary

MeasureTime frameDescription
Phase 2b: Evaluate response rates in patients treated with the combination of BXCL701 + PEMBRO and with BXCL701 monotherapyup to 36 monthsTo evaluate the response rates, defined by RECIST 1.1 criteria, by histologic subtype in patients treated with the combination of BXCL701 + PEMBRO and with BXCL701 monotherapy.
Phase 2a: Estimate the composite response rate of the combination of BXCL701 + PEMBROup to 36 monthsResponse Evaluation Criteria In Solid Tumors (RECIST) 1.1 criteria; circulating tumor cell (CTC) conversion from \>5/7.5 mL to \<5/7.5 mL per Veridex assay; and 50% or greater prostate-specific antigen (PSA) decline from baseline.

Secondary

MeasureTime frameDescription
Phase 2a: Estimate the median PSA progression-free survival (PSA PFS) of the combination of BXCL701 and PEMBRO in Cohort A and B.up to 36 monthsThe median time frame with progression-free survival with the use of BXCL701 in combination with Pembro
Phase 2a: Estimate the median overall survival (OS) of the combination of BXCL701 and PEMBRO in Cohort A and B.up to 36 monthsThe median time frame with overall survival with the use of BXCL701 in combination with Pembro
Phase 2a: Estimate the median duration of response (DOR) of the combination of BXCL701 and PEMBRO in Cohort A and B.up to 36 monthsThe timeframe in which the tumor reacts to BXCL701 in combination with Pembro
Phase 2a: Determine the risk profile of the use of BXCL701 in combination with PEMBRO.up to 36 monthsDetermines the frequency and severity of known and unknown adverse events with the use of BXCL701 in combination with Pembro
Phase 2a: Assess population pK of BXCL701Up to 36 monthsTo assess the population pharmacokinetics of BXCL701 using sparse pharmacokinetic sampling.
Phase 2b: Estimate the CRR, OS, duration response, rPFS and PSA PFS of the BXCL701+Pembro.Up to 36 monthsTo estimate the CRR, OS, duration of response, rPFS, and PSA PFS of the BXCL701 + PEMBRO combination and monotherapy in Cohort A and B, respectively. Composite response rate is defined as achieving 1 or more of the following: * Objective response by Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 criteria * 50% or greater PSA decline from baseline.
Phase 2a: Assess pharmacodynamic profile of BXCL701 and PembroUp to 36 monthsTo assess the pharmacodynamic profile of the combination of BXCL701 and PEMBRO by measuring relevant effects on those cytokines previously shown to be modulated by BXCL701 in humans.
Phase 2a: Estimate the median radiographic progression-free survival (rPFS) of the combination of BXCL701 and PEMBRO in Cohort A and Bup to 36 monthsThe median time frame with progression-free survival with the use of BXCL701 in combination with Pembro determined by radiographic evidence.

Countries

United Kingdom, United States

Contacts

STUDY_DIRECTORAmir Hafeez, MD

Bioxcel Therapeutics

STUDY_CHAIRVincent O'Neill, MD

Bioxcel Therapeutics

Outcome results

None listed

Source: ClinicalTrials.gov · Data processed: May 16, 2026