A Study of JNJ-101556143 in Participants With Metastatic Prostate Cancer

About This Trial

This study is testing an experimental medicine to see if it can shrink or stop tumors in men with advanced prostate cancer.
It is designed for people whose cancer has spread to other parts of the body and is continuing to grow despite standard hormone therapy.
Before joining, you will need imaging scans showing that your cancer is active, and you must pause any other cancer treatments for a few weeks while continuing your regular hormone-lowering therapy.
Patients who have had recent major surgery or have serious liver, kidney, or pancreas problems are not eligible to take part.

More Information

The purpose of this study is to evaluate how well JNJ-101556143 works in participants with metastatic androgen pathway modulation-resistant prostate cancer (mAPMR), an advanced form of prostate cancer that has spread and no longer responds to hormone therapy.
The study will measure the overall response (tumor shrinkage or disappearance) following treatment with JNJ-101556143.

Who Can Enroll

Age Range: 18 years and older
Gender: Male
Who This Trial is For: This study is testing an experimental medicine to see if it can shrink or stop tumors in men with advanced prostate cancer.

Study Details

Start Date: September 16, 2026
Lead Sponsor: Janssen Research & Development, LLC

Full Eligibility Criteria

Inclusion Criteria

Have histologically confirmed adenocarcinoma of the prostate. Primary (or pathologic evidence of conversion to) small cell carcinoma, carcinoid tumor, mixed neuroendocrine carcinoma, large cell neuroendocrine carcinoma, or sarcoma of the prostate is disallowed
Progressive metastatic androgen pathway modulation-resistant prostate cancer (mAPMR) defined as having a Prostate-Specific Antigen (PSA) level greater than or equal (>=) 10 nanograms per milliliter (ng/mL) and at least one of the following: (a) PSA progression defined as at least 2 consecutive increases in PSA value over a previous reference value measured at least 1 week apart. (b) Progressive disease or new lesion(s) in the lymph nodes, bones, or viscera on conventional imaging (computed tomography [CT]/magnetic resonance imaging [MRI]) as defined by response evaluation criteria in solid tumors version 1.1 (RECIST v1.1) and/or on bone scan per Prostate Cancer Working Group 4 (PCWG4) while on Androgen Deprivation Therapy (ADT) (either surgically [bilateral orchiectomy] or with medication). Local-regional disease including invasive disease of rectum, bladder, pelvis is allowed as long as participant has a current or past history of distant metastasis (M1 disease). Participants in Part 1 must have measurable disease per RECIST v1.1 by conventional imaging with CT or MRI (chest, abdomen, and pelvis) and/or Technetium-99^m (99^mTc) bone scan confirmed by Blinded Independent Central Review (BICR) at the time of screening
Prior bilateral orchiectomy or medical castration (receiving ongoing ADT with a Gonadotropin-Releasing Hormone (GnRH) analog [agonist or antagonist]) with castrate level of serum testosterone (less than [<] 50 nanograms per deciliter [ng/dL] or 1.7 nanomoles per liter [nmol/L]) prior to the first dose of trial intervention and must continue this therapy throughout the treatment phase
Have discontinued concurrent use of any non-investigational systemic anticancer therapy (that is, cytotoxic chemotherapy, Androgen Receptor Pathway Inhibitor (ARPI), radiation therapy) within 2 weeks or Lutetium-177 Prostate-Specific Membrane Antigen-617 (177^Lu PSMA-617) within 6 weeks prior to first dose of trial intervention, or any investigational drugs within 3 months of first dose of trial intervention
Toxicity related to prior anticancer treatment that is deemed clinically relevant must have resolved to common terminology criteria for adverse events (CTCAE) Version 6.0 Grade 1 or better

Exclusion Criteria

Acute or chronic uncontrolled renal disease, pancreatitis, or liver disease (with exception of patients with Gilbert's Syndrome, asymptomatic gallstones, liver metastases, or stable chronic liver disease per investigator assessment)
Suspected or known allergies, hypersensitivity, or intolerance to JNJ-101556143 or its excipients
Had major surgery or had significant traumatic injury less than or equal to 28 days of the first dose of trial intervention. Note: Participants with planned surgical procedures to be conducted under local anesthesia may participate
Spinal cord compression unless considered to have received definitive treatment for this and evidence of clinically stable disease for 28 days
Solid organ or bone marrow transplantation