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Microsatellite Stable Rectal CarcinomaPhase 2NCT06843434

A Study of Botensilimab and Balstilimab for Rectal Adenocarcinoma

A Phase 2 study testing Balstilimab and Botensilimab in people with Microsatellite Stable Rectal Carcinoma and Locally Advanced Rectal Adenocarcinoma, run by Memorial Sloan Kettering Cancer Center at 7 sites in United States.

Recruiting

Looking for participants now. Contact the study team or a site below to ask about taking part.

Sites and contacts
Official record
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Trial summary

The purpose of this study is to find out whether the combination of botensilimab and balstilimab (BOT/BAL) is a safe and effective treatment that causes few or mild side effects for people with mismatch repair proficient (MMRp)/microsatellite stable (MSS) locally advanced rectal adenocarcinoma. Read more about this study

Who is it for?
Ages 18 years and older
What is being tested?
Balstilimab and Botensilimab
Could I receive a placebo?
No, everyone receives an active treatment
How many people
40 participants
Where
7 sitesUnited States
Study dates
20 Feb 2025to 20 Feb 2028
Phase
Phase 2
Are there results?
Not yet: the study is under way

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 18 years and older
  • All sexes
  • No healthy volunteers
  • Adult, Older adult

Who may be able to join

  • Willing and able to provide written informed consent for trial.
  • If participant is unable to provide written informed consent, the legally authorized representative (LAR) of the person who is being asked to participate in this research study may give consent on the participant's behalf.
  • Be ≥18 years of age on the date of signing informed consent.
  • ECOG performance status of 0 or 1.
  • Histologically confirmed rectal adenocarcinoma.
  • Adenocarcinoma with distal margin of 15 cm or less from the anal verge on endoscopy, staged with endorectal ultrasound (ERUS) or magnetic resonance imaging (MRI) as cT3/cT4 N0 or cT(any) cN1/2.
Show all 18Show fewer
  • No evidence of distant metastases
  • Radiologically measurable or clinically evaluable disease per Protocol Section 13.0.
  • Tumor specimen that demonstrates intact mismatch repair enzymes by immunohistochemistry or microsatellite stability as demonstrated by NGS or PCR.
  • Negative pregnancy test done within 14 days prior to beginning treatment, for women of childbearing potential only. Subjects of childbearing potential must be willing to use an adequate method of contraception. Appropriate methods of birth control include abstinence, oral contraceptives, implantable hormonal contraceptives, or double barrier method (diaphragm plus condom). Contraception is required for the course of the study starting with the first dose of study medication through 150 days after the last dose of study medication. Note: Abstinence is acceptable if this is the usual lifestyle and preferred contraception for the subject.
  • Nonchildbearing potential is defined as follows (by other than medical reasons):
  • ≥45 years of age and has not had menses for >1 year
  • Patients who have been amenorrhoeic for <2 years without history of a hysterectomy and oophorectomy must have a follicle stimulating hormone value in the postmenopausal range upon screening evaluation
  • Post-hysterectomy, post-bilateral oophorectomy, or post-tubal ligation. Documented hysterectomy or oophorectomy must be confirmed with medical records of the actual procedure or confirmed by an ultrasound. Tubal ligation must be confirmed with medical records of the actual procedure, otherwise the patient must be willing to use 2 adequate barrier methods throughout the study.
  • Demonstrate adequate organ function as defined in the Table 6-1 below within 28 days of Cycle 1 Day 1, and all screening labs should be performed within 28 days of treatment initiation.
  • Hematological Absolute neutrophil count (ANC): ≥1,500 /mm^3 Platelets: ≥100,000 / mcL Hemoglobin: ≥8.0 g/dL
  • Renal Serum creatinine OR measured or calculated creatinine clearance (GFR can also be used in place of creatinine or CrCl): ≤1.5 × upper limit of normal (ULN) OR ≥60 mL/min for subject with creatinine levels > 1.5 × institutional ULN AST (SGOT) and ALT (SGPT): ≤ 2.5 × ULN
  • Coagulation International normalized ratio (INR) or Prothrombin time (PT) or activated partial thromboplastin time (aPTT): For patients not taking warfarin: INR ≤ 1.5 or PT ≤ 1.5 x ULN; and either PTT or aPTT ≤ 1.5 x ULN. Patients on warfarin may be included on a stable dose with a therapeutic INR <3.5

Who cannot join

  • Recurrent rectal cancer.
  • Prior pelvic radiation therapy, chemotherapy, or surgery for rectal cancer.
  • Tumor is causing symptomatic bowel obstruction (patients who have a temporary diverting ostomy are eligible).
  • Other invasive malignancy ≤ 2 years prior to registration. Exceptions are non-melanoma skin cancer that has undergone potentially curative therapy and in situ cervical carcinoma.
  • Active infection requiring systemic therapy.
  • Other anticancer or experimental therapy. No other experimental therapies (including chemotherapy, radiation, hormonal treatment, antibody therapy, immunotherapy, gene therapy, vaccine therapy, angiogenesis inhibitors, matrix metalloprotease inhibitors, thalidomide, anti-VEGF/Flk-1 monoclonal antibody or other experimental drugs) of any kind are permitted while the patient is receiving study treatment.
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  • Known history of interstitial lung diseases/pneumonitis
  • Known history of human immunodeficiency virus (HIV) (HIV 1/2 antibodies)
  • Known active hepatitis B (e.g., HbsAg reactive) or hepatitis C (e.g., HCV RNA [qualitative] is detected).
  • Live vaccination within 28 days prior to receiving the first dose of immunotherapy. The use of inactivated seasonal influenza vaccines (e.g., Fluzone®) will be permitted on study without restriction.
  • Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine or booster < 7 days before C1D1. For vaccines requiring more than 1 dose, the full series should be completed prior to C1D1, when feasible. Booster shot not required but also must be administered > 7 days from C1D1 or > 7 days from future cycle on study
  • Clinically significant (i.e., active) cardiovascular disease: cerebral vascular accident/stroke or myocardial infarction within 180 days of enrollment, unstable angina, congestive heart failure (New York Heart Association class ≥ III), or serious uncontrolled cardiac arrhythmia requiring medication.
  • QTcF (QT interval corrected using Fridericia's formula) of ≥450 ms.
  • Known active tuberculosis.
  • Receiving systemic corticosteroid therapy 1 week prior to the first dose of study drug or receiving any other form of systemic immunosuppressive medication.
  • Corticosteroid use as a premedication for IV contrast allergies/reactions is allowed. Subjects who are receiving daily corticosteroid replacement therapy are also an exception to this rule. Daily prednisone at doses of ≤ 7.5 mg or equivalent hydrocortisone dose are examples of permitted replacement therapy. Use of inhaled or topical corticosteroids is permitted.
  • Has ongoing or recent (within 5 years) evidence of significant autoimmune disease or any other condition that required treatment with systemic immunosuppressive treatments. The following are not exclusionary: vitiligo, childhood asthma that has resolved, endocrinopathies (such as hypothyroidism or type 1 diabetes) that require only hormone replacement.
  • Prior allogeneic tissue/solid organ transplant, except for corneal transplants.

Trial locations and contacts

7 sites in 1 country. Contact the study team or a site near you to ask about taking part.

Andrea Cercek, MD contact

646-888-4189

cerceka@mskcc.org

Paul Romesser, MD contact

646-888-2118

romessep@mskcc.org

7 sites in 1 country

United States7 sites, 7 recruiting

  • Memorial Sloan Kettering Basking Ridge (Limited Protocol Activities)

    Basking Ridge, New Jersey, 07920

    Andrea Cercek, MD, 646-888-4189

    Andrea Cercek, MD

    Recruiting

  • Memorial Sloan Kettering Cancer Center at Suffolk - Commack (Limited Protocol Activities)

    Commack, New York, 11725

    Andrea Cercek, MD, 646-888-4189

    Recruiting

  • Memorial Sloan Kettering Westchester (Limited Protocol Activities)

    Harrison, New York, 10604

    Andrea Cercek, MD, 646-888-4189

    Recruiting

  • Memorial Sloan Kettering Monmouth (Limited Protocol Activities)

    Middletown, New Jersey, 07748

    Andrea Cercek, MD, 646-888-4189

    Recruiting

  • Memorial Sloan Kettering Bergen (Limited Protocol Activities)

    Montvale, New Jersey, 07645

    Andrea Cercek, MD, 646-888-4189

    Recruiting

  • Memorial Sloan Kettering Cancer Center (All Protocol Activities)

    New York, New York, 10065

    Andrea Cercek, MD, 646-888-4189

    Andrea Cercek, MD

    Recruiting

  • Memorial Sloan Kettering Nassau (Limited Protocol Activities)

    Uniondale, New York, 11553

    Andrea Cercek, MD, 646-888-4189

    Recruiting

Other trials in United States

About this study

Official title: A Phase II Study of Neoadjuvant Botensilimab and Balstilimab Immunotherapy for Mismatch Repair Proficient Rectal Adenocarcinoma

The purpose of this study is to find out whether the combination of botensilimab and balstilimab (BOT/BAL) is a safe and effective treatment that causes few or mild side effects for people with mismatch repair proficient (MMRp)/microsatellite stable (MSS) locally advanced rectal adenocarcinoma. The investigators will also find out whether BOT/BAL is an effective treatment when given in combination with standard chemotherapy.

Being tested
Balstilimab, Botensilimab
Keywords
Microsatellite Stable Rectal Carcinoma, mismatch repair proficient locally advanced rectal adenocarcinoma, locally advanced rectal adenocarcinoma, microsatellite stable locally advanced rectal adenocarcinoma, Memorial Sloan Kettering Cancer Center, 24-389

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • BalstilimabDrug

    Balstilimab is a fully human monoclonal IgG4 antibody designed to block PD-1 binding to PD-L1 and PD-L2

  • BotensilimabDrug

    Botensilimab is a novel fully human fragment crystallizable (Fc)-engineered immunoglobulin 1 kappa (IgG1κ) anti-CTLA-4 immunoglobulin G1 (IgG1) antagonist antibody that is designed to optimally promote fragment-crystallizable gamma receptor (FcγR) effector functions that are important for enhancing T cell priming and regulatory T cell (Treg) depletion.

Study groups in NCT06843434
Study groupRoleWhat they receive
Participants with locally advanced rectal cancerExperimentalUp to 40 patients with mismatch repair proficient (MMRp)/microsatellite stable (MSS) locally advanced (stage II or III) rectal cancer
Receives: Drug: Balstilimab; Drug: Botensilimab

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Best Overall Response Rate

    The primary objective of this study is to determine the best overall response rate (ORR) after initial neoadjuvant combination botensilimab and balstilimab in subjects with MMRp/MSS locally advanced (stage II or III) rectal adenocarcinoma. ORR is defined by rectal MRI and endoscopic exam and graded as progressive disease (PD), stable disease (SD) (sustained for 3 months), partial response (PR), near complete response (nCR) and clinical complete response (cCR). Patients with PR, nCR, or cCR will be considered responders, while the rest will be non-responders.

    Measured: 1 year

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted25 Feb 2025
  2. Study start20 Feb 2025
  3. Primary completion20 Feb 2028 (estimated)
  4. Study completion20 Feb 2028 (estimated)

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Phase 2
Primary purpose
Treatment
Allocation
Not applicable
Intervention model
Single group
Masking
None (open label)
Enrolment
40 participants (estimated)
IDs, dates and publications
ClinicalTrials.gov ID
NCT06843434
Sponsor's protocol ID
24-389
Status last verified
Jun 2026
First submitted
20 Feb 2025
Last updated
16 Jun 2026
Results posted
No
Data monitoring committee
Yes
FDA-regulated drug
Yes
FDA-regulated device
No
Individual data sharing
Yes: Memorial Sloan Kettering Cancer Center supports the international committee of medical journal editors (ICMJE) and the ethical obligation of responsible sharing of data from clinical trials. The protocol summary, a statistical summary, and informed consent form will be made available on clinicaltrials.gov when required as a condition of Federal awards, other agreements supporting the research and/or as otherwise required. Requests for deidentified individual participant data can be made beginning 12 months after publication and for up to 36 months post publication. Deidentified individual participant data reported in the manuscript will be shared under the terms of a Data Use Agreement and may only be used for approved proposals. Requests may be made to: crdatashare@mskcc.org.

Questions about this trial

What is this clinical trial studying?

A Phase 2 study testing Balstilimab and Botensilimab in people with Microsatellite Stable Rectal Carcinoma and Locally Advanced Rectal Adenocarcinoma, run by Memorial Sloan Kettering Cancer Center at 7 sites in United States.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 18 inclusion and 18 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: looking for participants now, as of the sponsor's last update on 16 Jun 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 7 sites in United States. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

What does this phase mean?

Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

This study is still under way. Results are not available in the source record yet.

How can a doctor refer a patient or contact the research team?

Contact Andrea Cercek, MD (646-888-4189, cerceka@mskcc.org), or a site near the patient. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Best Overall Response Rate (time frame: 1 year). It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT06843434.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 16 Jun 2026.

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