A Phase 2 interventional study of Pembrolizumab and Porustobart in Colon Cancer, sponsored by Solstice Oncology, Inc.. Recruiting at 30 sites in 6 countries. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-10-27.
Sponsored by Solstice Oncology, Inc. · Phase 2, Interventional, and Treatment
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
2,457 studies on the registry are indexed under Colonic Neoplasms; 458 are open to participants now.
This study's planned enrollment of 100 is above the median of 75 across 1,711 interventional studies indexed under Colonic Neoplasms.
Browse Colonic Neoplasms studies →This is the only study on the registry with Solstice Oncology, Inc. as lead sponsor.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
≥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
Performance Status 0-1
Adequate tumor tissue sample with associated pathology report
Adequate hematologic, hepatic, and renal function
Reproductive status/ requirements per protocol
Exclusion Criteria:
agent within 3 weeks of first dose
Imminent or urgent need for surgery
Prior treatment with ICIs targeting , PD-1, or PD-L1
Systemic / therapy within 1 week of first dose (exceptions apply)
History of severe to a fully human mAb; interstitial lung disease; pneumonitis requiring corticosteroids
Active or history of disease requiring systemic treatment within 2 years
Major surgery within 4 weeks of first dose; active infection requiring treatment
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
PD-1, PD-L1 and CTLA-4 are proteins that act as brakes on the immune system. Checkpoint inhibitors, such as pembrolizumab or nivolumab, block them so the immune system can attack a cancer.
PD-L1 can also be measured in a tumour sample. Some scores count stained tumour cells only (TPS); others also count certain immune cells (CPS). The study names the score and the minimum it uses.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
ECOG performance status
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraception
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
PD-1, PD-L1 and checkpoint inhibitors
PD-1, PD-L1 and CTLA-4 are proteins that act as brakes on the immune system. Checkpoint inhibitors, such as pembrolizumab or nivolumab, block them so the immune system can attack a cancer.
PD-L1 can also be measured in a tumour sample. Some scores count stained tumour cells only (TPS); others also count certain immune cells (CPS). The study names the score and the minimum it uses.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Immunosuppression
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Autoimmune disease
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Pembrolizumab IV every 3 weeks x 2 doses (Day 1, Day 22) plus porustobart x 1 dose (Day 1 only)
Drug: Pembrolizumab · Drug: Porustobart
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
Administered to: Dose Schedule 1 - Porustobart + Pembrolizumab, Dose Schedule 2 - Porustobart + Pembrolizumab
Also known as: Keytruda
Administered to: Dose Schedule 1 - Porustobart + Pembrolizumab, Dose Schedule 2 - Porustobart + Pembrolizumab
Also known as: HBM4003
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
Time frame: Assessed from surgical resection specimen (surgery occurs Day 42-Day 63, i.e., approximately Week 6-Week 9 after first dose)
Pathologic Complete Response (pCR) rate
Time frame: Assessed from surgical resection specimen (Week 6-9)
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)
Start is estimated for Sep 2026; primary completion for Sep 2029, 36 months later.
Of 135 phase 2 interventional studies under Colonic Neoplasms, half reached primary completion within 43 months of starting (the median), counting those still running; a quarter within 30 and three quarters within 66. This study's planned 36 months is below that.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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Studies of the drug tested here: Porustobart