Recruiting
Phase 2

Porustobart & Pembrolizumab

Sponsor:

Solstice Oncology, Inc.

Code:

NCT07808151

Conditions

Colon Cancer

Eligibility Criteria

Sex: All

Age: 18+

Healthy Volunteers: Not accepted

Interventions

Pembrolizumab

Porustobart

Study Details

Brief summary:

The goal of this clinical trial is to learn if giving two medicines together, porustobart and pembrolizumab, before surgery can treat a common type of colon cancer called microsatellite stable (MSS) colon cancer in adults. This type of cancer can be removed with surgery and has not spread to other parts of the body. Both medicines work by helping the immune system fight cancer.

The main questions this study wants to answer:

How well do the medicines destroy the cancer before surgery? What side effects do participants have when taking the medicines?

Researchers will compare two groups to see which treatment schedule works better and is safer. Both groups get pembrolizumab. One group gets one dose of porustobart (Day 1 only), and the other group gets two doses (Day 1 and Day 22).

Participants will:

Complete certain tests and procedures to make sure they are eligible Get the medicines through a vein on Day 1 and Day 22 then have surgery 6-9 weeks after starting treatment Return for checkups and tests every 6 months for up to 3 years after surgery

Conditions

Colon Cancer

Study ID

NCT07808151

Start date

Sep 30, 2026

Status verified date

Oct, 2026

Completion date

Sep 30, 2029

Anticipated

Primary completion date

Sep 30, 2029

Anticipated

Eligibility Criteria

Eligibility Criteria

Sex: All

Age: 18+

Healthy Volunteers: Not accepted

Inclusion Criteria:

≥18 years of age at consent

Adenocarcinoma of the colon (rectosigmoid considered non-rectal); pMMR/MSS status

Any T3 or T4, N any, M0; disease amenable to surgical resection

ECOG Performance Status 0-1

Adequate tumor tissue sample with associated pathology report

Adequate hematologic, hepatic, and renal function

Reproductive status/contraception requirements per protocol

Exclusion Criteria:

Investigational agent within 3 weeks of first dose

Imminent or urgent need for surgery

Prior treatment with ICIs targeting CTLA-4, PD-1, or PD-L1

Systemic corticosteroid/immunosuppressive therapy within 1 week of first dose (exceptions apply)

History of severe hypersensitivity to a fully human mAb; interstitial lung disease; pneumonitis requiring corticosteroids

Active or history of autoimmune disease requiring systemic treatment within 2 years

Major surgery within 4 weeks of first dose; active infection requiring treatment

Study Design

Enrollment

100 participants

Anticipated

Allocation

Randomized

Intervention Model

Parallel Assignment

Primary purpose

Treatment

Interventions and Outcome Measures

Arms

experimental: Dose Schedule 1 - Porustobart + Pembrolizumab

Pembrolizumab IV every 3 weeks x 2 doses (Day 1, Day 22) plus porustobart x 1 dose (Day 1 only)

experimental: Dose Schedule 2 - Porustobart + Pembrolizumab

Pembrolizumab IV every 3 weeks x 2 doses (Day 1, Day 22) plus porustobart every 3 weeks x 2 doses (Day 1, Day 22)

Interventions

Pembrolizumab

Administered to: Dose Schedule 1 - Porustobart + Pembrolizumab, Dose Schedule 2 - Porustobart + Pembrolizumab

Porustobart

Administered to: Dose Schedule 1 - Porustobart + Pembrolizumab, Dose Schedule 2 - Porustobart + Pembrolizumab

Primary outcome measure

  • Major Pathologic Response (MPR) rate by Blinded Independent Pathologic Review (BIPR) [ Time Frame: Assessed from surgical resection specimen (surgery occurs Day 42-Day 63, i.e., approximately Week 6-Week 9 after first dose) ]

Central Contacts and Locations

Central contacts

Medical Monitor

617-982-2331SOL1-201@solsticeoncology.com

Locations

Investigator Site

Recruiting

Seattle, Washington, United States, 98109

More Information

Sponsor

Solstice Oncology, Inc.

Last update posted

Oct 22, 2026

Last verified

Oct, 2026

Keywords

  • neoadjuvant therapy
  • Immune checkpoint inhibitor
  • CTLA-4
  • PD-1
  • Porustobart
  • HBM4003
  • Pembrolizumab
  • Major pathologic response
  • pMMR/MSS colon cancer
  • Resectable colon cancer
  • Fc-enhanced CTLA-4
  • Microsatellite Stable (MSS) Colon Cancer
  • Proficient Mismatch Repair (pMMR) Colon Cancer

Trial information was received from ClinicalTrials.gov and was last updated on 2026-10-23. This information was provided to ClinicalTrials.gov by Solstice Oncology, Inc. on 2026-10-22. Recruitment status is synced daily from ClinicalTrials.gov and may not reflect the sponsor's current status. Confirm during your call.