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NCT Number: NCT07808151

Neoadjuvant Pembrolizumab and Porustobart in Resectable pMMR/MSS Colon Cancer

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

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Key information

Conditions

Colon Cancer Brain Diseases Central Nervous System Diseases Cerebellar Diseases Colonic Diseases Colonic Neoplasms Colorectal Neoplasms Congenital, Hereditary, and Neonatal Diseases and Abnormalities Diabetes Mellitus, Insulin-Dependent, 12 Digestive System Diseases Digestive System Neoplasms Gastrointestinal Diseases Gastrointestinal Neoplasms Genetic Diseases, Inborn Heredodegenerative Disorders, Nervous System Intestinal Diseases Intestinal Neoplasms Microsatellite Stable (MSS) Colon Cancer Neoplasms Neoplasms by Site Nervous System Diseases Neurodegenerative Diseases Proficient Mismatch Repair (pMMR) Colon Cancer Spinal Cord Diseases Spinocerebellar Degenerations

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 2

Primary location

Investigator Site, Anderlecht, Belgium

Loading trial locations.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

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

Treatment and study plan

Pembrolizumab

Drug

Administered to: Arm 1, Arm 2

Other names: Keytruda

Porustobart

Drug

Administered to: Arm 1, Arm 2

Other names: HBM4003

Primary outcomes

  1. 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)

    MPR is defined as the proportion of patients with ≤10% residual tumor volume in the primary tumor and lymph nodes, as evaluated by BIPR, per treatment arm

Secondary outcomes

  1. Pathologic Complete Response (pCR) rate

    Time frame: Assessed from surgical resection specimen (Week 6-9)

  2. Incidence of treatment-related adverse events (AEs), serious adverse events (SAEs), and immune-related AEs

    Time frame: From informed consent through 60 days after last dose (or initiation of new anti-cancer treatment, whichever occurs first)

Study contacts

Contact information is provided by the study sponsor or research team.

Medical Monitor

CONTACT

[email protected]

617-982-2331

Sponsors and collaborators

Lead sponsor

Solstice Oncology, Inc.

Industry

Registry information

Official study title

A Phase 2, Open-Label, Multicenter, Randomized Trial Evaluating the Efficacy and Safety of Different Schedules of Neoadjuvant Pembrolizumab and Porustobart in Patients With Resectable pMMR/MSS Colon Cancer

Important dates

Study start
2026
Primary completion
2029
Study completion
2029
First posted
Sep 8, 2026
Registry last updated
Sep 8, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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