GI-102 (CD80-IgG4 Fc-IL2v3) in Combination With Pasritamig in Patients With Metastatic Castration-resistant Prostate Cancer (mCRPC) (JET-201)

Participants receive GI-102 in combination with pasritamig during the Safety run-in phase. Dose escalation is guided by a Bayesian Optimal Interval (BOIN) design.

GI-102 will be administered in accordance with the procedures specified in the study protocol.

Pasritamig will be administered in accordance with the procedures specified in the study protocol.

Participants receive GI-102 in combination with pasritamig during the Safety run-in phase. Dose escalation is guided by a Bayesian Optimal Interval (BOIN) design.

GI-102 will be administered in accordance with the procedures specified in the study protocol.

Pasritamig will be administered in accordance with the procedures specified in the study protocol.

Participants enrolled in the Expansion phase will receive the combination recommended Phase 2 regimen (cRP2R) of GI-102 and pasritamig, determined based on the safety and dose-escalation results from the Safety run-in phase.

GI-102 will be administered in accordance with the procedures specified in the study protocol.

Pasritamig will be administered in accordance with the procedures specified in the study protocol.

A DLT is defined as a clinically significant AE (classified according to the NCI CTCAE version 6.0) or significant laboratory abnormality that occur during the DLT assessment periods, and is considered by the Investigator to be related to the study drug(s).

An adverse event (AE) is any untoward medical occurrence in a participant administered a pharmaceutical product and which does not necessarily have to have a causal relationship with the treatment. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding, for example), symptom, or disease temporally associated with the use of a pharmaceutical product, whether or not considered related to the pharmaceutical product. Preexisting conditions which worsen during a study are also considered as AEs. All AE events will be graded according to National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events (CTCAE) version 6.0.

PSA response rate is defined as the percentage of participants with a decline of PSA of 50% or more from baseline.

PSA response rate is defined as the percentage of participants with a decline of PSA of 50% (or 90%) or more from baseline.

Radiographic PFS is defined as the time from the date of first dose of any study treatment until the date of radiographic disease progression or death, whichever comes first.

Time to PSA progression, defined as the time from baseline to the first date of documented PSA progression per PCWG3 criteria.

Among participants with measurable disease, ORR is defined as the percentage of participants who achieve a partial response (PR) or complete response (CR) according to RECIST v1.1.

Among participants with measurable disease who achieve a CR or PR, DoR is defined as the time from the first documented CR or PR until the first documented disease progression according to RECIST v1.1 or death from any cause, whichever occurs first.

Among participants with measurable disease, DCR is defined as the percentage of participants who achieve a CR, PR, or stable disease (SD) according to RECIST v1.1.

An adverse event (AE) is any untoward medical occurrence in a participant administered a pharmaceutical product and which does not necessarily have to have a causal relationship with the treatment. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding, for example), symptom, or disease temporally associated with the use of a pharmaceutical product, whether or not considered related to the pharmaceutical product. Preexisting conditions which worsen during a study are also considered as AEs. All AE events will be graded according to National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events (CTCAE) version 6.0.

Plasma concentrations of GI-102 will be measured at specified time points following administration of GI-102 in combination with pasritamig to determine the maximum observed plasma concentration (Cmax).

Plasma concentrations of GI-102 will be measured at specified time points following administration of GI-102 in combination with pasritamig to determine the terminal half-life (T1/2) of GI-102.

Plasma concentrations of GI-102 will be measured at specified time points following administration of GI-102 in combination with pasritamig to determine the area under the plasma concentration-time curve (AUC) of GI-102.

Immune cell populations and their changes following study treatment will be assessed in peripheral blood using flow cytometry.

ORR is defined as the percentage of participants who achieve a partial response (PR) or complete response (CR) according to the iRECIST criteria.

Overall survival (OS) is defined as the time from the first dose of study treatment to death from any cause.

Serum samples will be analyzed using a validated assay to determine the incidence of anti-GI-102 antibodies (ADA).

Serum samples that are positive for anti-GI-102 antibodies (ADA) will be further analyzed using a validated assay to determine the incidence of neutralizing antibodies (Nab).