Trial Outcomes & Findings for A Study of Zalifrelimab and Balstilimab for Treatment of Participants With Metastatic or Locally Advanced Solid Tumors, and Expansion Into Select Solid Tumors (Cervical) (NCT NCT03495882)

The trial was conducted at 46 trial centers.

A Study of Zalifrelimab and Balstilimab for Treatment of Participants With Metastatic or Locally Advanced Solid Tumors, and Expansion Into Select Solid Tumors (Cervical)

The ORR was defined as the percentage of participants with a confirmed best overall response (BOR) of partial response (PR) or complete response (CR), as determined by an IERC per Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST 1.1).

The number of participants with an occurrence of a DLT during dose escalation during the first 21 days of treatment in Phase 1 are reported. Any DLT immediately led to permanent withdrawal of zalifrelimab and balstilimab.

Blood samples were collected for serum balstilimab and zalifrelimab concentration analyses. Each cycle was 6 weeks (42 days) long. Results are reported as micrograms/milliliter (ug/mL).

Blood samples were collected for serum balstilimab and zalifrelimab concentration analyses. Each cycle was 6 weeks (42 days) long.

Blood samples were collected for serum balstilimab and zalifrelimab concentration analyses. Each cycle was 6 weeks (42 days) long. Results are reported as day times ug/mL (day\*ug/mL).

Blood samples were collected for serum balstilimab and zalifrelimab concentration analyses. Each cycle was 6 weeks (42 days) long.

Blood samples were collected for serum balstilimab and zalifrelimab ADA determination.

The ORR was defined as the percentage of participants with a confirmed BOR of PR or CR, as determined by the investigator per RECIST 1.1.

DOR was defined as time from first observation of response to first observation of documented disease progression (or death within 12 weeks after last tumor assessment), as determined by an IERC and investigator, per RECIST 1.1. Participants without an event at the analysis cutoff date were censored on date of last tumor assessment. DOR data are reported as 25th percentile estimated from Kaplan-Meier curve.

DCR was defined as the percentage of participants with CR, PR, or stable disease (SD) without progressive disease (PD) within 81 days of study start, or durable SD following PD, as determined by an IERC and investigator, per RECIST 1.1.

TTR was defined as the time interval between the date of treatment initiation and the earliest date of first documented confirmed complete response or partial response based on independent radiologic review, as determined by an IERC per RECIST 1.1.

PFS was defined as the interval from the date of first dose of investigational agent until the earliest date of PD, as determined by IERC and investigator assessment of objective radiographic disease assessments per RECIST 1.1, or death due to any cause if occurring sooner than progression.

OS was defined as the interval from the date of first dose of investigational agent until the date of death.

A validated flow cytometry-based assay was used to evaluate programmed cell death protein-1 (PD-1) RO on circulating T cells as an indication of target engagement of balstilimab. Blood samples were collected for the assay. Results are reported as a percentage of available drug receptors occupied (%RO) by balstilimab; the higher the percentage, the greater the engagement of balstilimab with the target receptor. Initial testing revealed technical limitations of the sample isolation procedure prior to the PD-1 RO assessment, causing the PD-1 RO assay to inaccurately reflect the actual PD-1 RO status in response to balstilimab/zalifrelimab combination treatment. As a result, further sample collection and subsequent testing was not conducted. Only initial test results are reported. Results reported as mean percentage of receptors occupied based upon data collected on Days 8, 15, 22, and 29 of Cycle 1 and Days 1 and 8 of Cycle 2 (each cycle was 6 weeks/42 days long).