Neoadjuvant Pembrolizumab and Porustobart in Resectable pMMR/MSS Colon Cancer

NCT07808151 | Not Yet Recruiting Phase 2 DMC FDA Drug

• 2 other identifiers: SOL1-2012026-527233-58-00
• Study Type: interventional
• Target: 100
• Locations: 6 countries
• Sites: 30

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; Microsatellite Stable (MSS) Colon Cancer; Proficient Mismatch Repair (pMMR) Colon Cancer

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

Outcome Measures

Primary Outcomes (1)

• Major Pathologic Response (MPR) rate by Blinded Independent Pathologic Review (BIPR)

  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

  Assessed from surgical resection specimen (surgery occurs Day 42-Day 63, i.e., approximately Week 6-Week 9 after first dose)

Secondary Outcomes (2)

• Pathologic Complete Response (pCR) rate

  Assessed from surgical resection specimen (Week 6-9)

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

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

Study Arms (2)

Arm 1

EXPERIMENTAL

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

Drug: Pembrolizumab; Drug: Porustobart

Arm 2

EXPERIMENTAL

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

Drug: Pembrolizumab; Drug: Porustobart

Interventions

Pembrolizumab DRUG

Administered to: Arm 1, Arm 2

Also known as: Keytruda

Arm 1; Arm 2

Porustobart DRUG

Administered to: Arm 1, Arm 2

Also known as: HBM4003

Arm 1; Arm 2

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• ≥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

You may not qualify if:

• 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

Sponsors & Collaborators

• Solstice Oncology, Inc.: lead

Study Sites (30)

Investigator Site

Los Angeles, California, 90033, United States

Location

Investigator Site

Tampa, Florida, 33612, United States

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Investigator Site

Chicago, Illinois, 60637, United States

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Investigator Site

Baltimore, Maryland, 21287, United States

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Investigator Site

Boston, Massachusetts, 02114, United States

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Investigator Site

New York, New York, 10016, United States

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New York, New York, 10021, United States

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New York, New York, 10027, United States

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Cleveland, Ohio, 44106, United States

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Nashville, Tennessee, 37232, United States

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Seattle, Washington, 98109, United States

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Anderlecht, Belgium

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Bonheiden, Belgium

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Ghent, Belgium

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Leuven, Belgium

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Liège, Belgium

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Ostend, Belgium

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Woluwe-Saint-Lambert, Belgium

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Milan, Italy

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Naples, Italy

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Pisa, Italy

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Amsterdam, Netherlands

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Barcelona, Spain

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L'Hospitalet de Llobregat, Spain

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Madrid, Spain

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Aberdeen, United Kingdom

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Cardiff, United Kingdom

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Glasgow, United Kingdom

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Leeds, United Kingdom

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Investigator Site

London, United Kingdom

Location

MeSH Terms

Conditions

Colonic Neoplasms; Spinocerebellar Degenerations; Diabetes Mellitus, Insulin-Dependent, 12

Interventions

pembrolizumab

Condition Hierarchy (Ancestors)

Colorectal Neoplasms; Intestinal Neoplasms; Gastrointestinal Neoplasms; Digestive System Neoplasms; Neoplasms by Site; Neoplasms; Digestive System Diseases; Gastrointestinal Diseases; Colonic Diseases; Intestinal Diseases; Cerebellar Diseases; Brain Diseases; Central Nervous System Diseases; Nervous System Diseases; Spinal Cord Diseases; Heredodegenerative Disorders, Nervous System; Neurodegenerative Diseases; Genetic Diseases, Inborn; Congenital, Hereditary, and Neonatal Diseases and Abnormalities

Central Study Contacts

Medical Monitor

CONTACT

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

Study Design

• Study Type: interventional
• Phase: phase 2
• Allocation: RANDOMIZED
• Masking: NONE
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: INDUSTRY
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: September 3, 2026
• First Posted: September 8, 2026
• Study Start: September 30, 2026
• Primary Completion (Estimated): September 30, 2029
• Study Completion (Estimated): September 30, 2029
• Last Updated: September 8, 2026

Record last verified: 2026-09

Locations

US (11); NL (1); ES (3); GB (5); BE (7); IT (3)