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Phase I

A Phase 1/2 Study of REGN5678 (Anti-PSMAxCD28) With Cemiplimab (Anti-PD-1) in Patients With Metastatic Castration-resistant Prostate Cancer

  • Study HIC#:2000029991
  • Last Updated:12/22/2022

The primary objectives of the study in Dose Escalation are to evaluate safety, tolerability, and pharmacokinetics (PK) of REGN5678 alone and in combination with cemiplimab and in Dose Expansion are to assess efficacy, as measured by objective response rate (ORR) per modified Prostate Cancer Working Group 3 (PCWG3) criteria, of REGN5678 in combination with cemiplimab.

The secondary objectives of the study in Dose Escalation are to assess efficacy, as measured by ORR per modified PCWG3 criteria, of REGN5678 in combination with cemiplimab and in Dose Expansion are to characterize the safety profile in each expansion cohort and to characterize the PK of REGN5678 in combination with cemiplimab. Secondary objectives in both Dose Escalation and Dose Expansion are to assess efficacy of REGN5678 in combination with cemiplimab, as measured by additional criteria and to assess immunogenicity of REGN5678 in combination with cemiplimab.

  • Start Date09/09/2022
  • End Date09/02/2025

Trial Purpose and Description

Primary Outcome Measures  :

  1. Incidence and severity of treatment-emergent adverse events (TEAEs) [ Time Frame: Through study completion, Up to 5 years ]Dose Escalation Phase
  2. Incidence and severity of adverse event of special interests (AESIs) [ Time Frame: Through study completion, Up to 5 years ]Dose Escalation Phase
  3. Incidence and severity of serious adverse events (SAEs) [ Time Frame: Through study completion, Up to 5 years ]Dose Escalation Phase
  4. Number of patients with grade ≥3 laboratory abnormalities [ Time Frame: Through study completion, Up to 5 years ]Dose Escalation Phase
  5. Incidence of dose-limiting toxicities (DLTs) [ Time Frame: First dose through day 42 of last patient in each dose level ]Dose Escalation Phase
  6. Concentration of REGN5678 in serum over time [ Time Frame: Through study completion, Up to 5 years ]Dose Escalation Phase
  7. Concentration of REGN5678 in combination with cemiplimab in serum over time [ Time Frame: Through study completion, Up to 5 years ]Dose Escalation Phase
  8. Objective response rate (ORR) per modified Prostate Cancer Working Group 3 (PCWG3) criteria [ Time Frame: Through study completion, Up to 5 years ]Dose Expansion Phase

Eligibility Criteria

Key Inclusion Criteria:

  • Histologically or cytologically confirmed adenocarcinoma of the prostate without pure small cell carcinoma
  • Metastatic, castration-resistant prostate cancer (mCRPC) with PSA value at screening

    ≥4 ng/mLthat has progressed within 6 months prior to screening as defined in the protocol

  • Has received ≥2 lines prior systemic therapy approved in the metastatic and/or castration-resistant setting (in addition to androgen deprivation therapy [ADT]) including at least one second-generation anti-androgen therapy (eg, abiraterone, enzalutamide, apalutamide, or darolutamide)

Key Exclusion Criteria:

  • Has received treatment with an approved systemic therapy within 3 weeks of dosing or has not yet recovered (ie, grade ≤1 or baseline) from any acute toxicities
  • Has received any previous systemic biologic therapy within 5 half-lives of first dose of study therapy
  • Has received prior PSMA-targeting therapy
  • Dose Expansion Only: Has had prior anti-cancer immunotherapy
  • Any condition that requires ongoing/continuous corticosteroid therapy (>10 mg prednisone/day or anti-inflammatory equivalent) within 1 week prior to the first dose of study therapy
  • Ongoing or recent (within 5 years) evidence of significant autoimmune disease that required treatment with systemic immunosuppressive treatments
  • Encephalitis, meningitis, neurodegenerative disease (with the exception of mild dementia that does not interfere with activities of daily living [ADLs]) or uncontrolled seizures in the year prior to first dose of study therapy
  • Uncontrolled infection with human immunodeficiency virus (HIV), hepatitis B or hepatitis C infection; or diagnosis of immunodeficiency

NOTE: Other protocol defined Inclusion/Exclusion Criteria apply