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Early Rectal CancerPhase 2RECTIFY-1NCT07735624

RECTIFY-1: Neoadjuvant Botensilimab + Balstilimab in MSS/pMMR Early Rectal Cancer

A Phase 2 study testing Botensilimab and Balstilimab in people with Early Rectal Cancer and Stage I Rectal Cancer, run by Dana-Farber Cancer Institute at 3 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
Search all trials

Trial summary

This is a multi-site, prospective, non-randomized phase 2 study evaluating neoadjuvant botensilimab in combination with balstilimab for patients with microsatellite stable (MSS) / mismatch repair proficient (MMRp) early rectal cancer staged T1-T2 N0 by MRI and considered candidates for surgical resection without… Read more about this study

Who is it for?
Ages 18 years and older
What is being tested?
Botensilimab and Balstilimab
Type of treatment
Injection or infusion
Could I receive a placebo?
No, everyone receives an active treatment
How many people
16 participants
Where
3 sitesUnited States
Study dates
10 Aug 2026to 31 Dec 2032
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

  • Histologically confirmed diagnosis of early-rectal cancer clinically staged T1-T2 N0 M0 by MRI (American Joint Committee on Cancer (AJCC) staging 8th edition, 2017).
  • The tumor must confirmed to be MSS/MMRp by local testing.
  • The tumor must be evaluable by endoscopy.
  • Voluntarily agree to participate by giving signed, dated, and written informed consent prior to any study-specific procedures.
  • Age ≥ 18 years of age. Because no dosing or adverse event data are currently available on the use of botensilimab with balstilimab in participants < 18 years of age, children are excluded from this study.
  • Measurable rectal primary on baseline imaging by MRI. The tumor must be definitively at least T1.
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  • Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.
  • Adequate organ function defined as the following laboratory values within 7 days of Cycle 1 Day 1 (C1D1):
  • Neutrophils ≥ 1500/μL (Must be stable and off any growth factor within 4 weeks of first study treatment administration).
  • Platelets ≥ 50× 103/μL.
  • Hemoglobin ≥ 8.0 g/dL (transfusion to achieve this level is not permitted within 2 weeks of first study treatment administration).
  • Creatinine clearance ≥ 30 mL/min as measured or calculated per local institutional standards.
  • Aspartate aminotransferase/alanine aminotransferase ≤ 1.5 × upper limit of normal (ULN).
  • Total bilirubin ≤ 1.5 × ULN (except patients with Gilbert syndrome who must have a total bilirubin level of ≤ 3.0 × ULN).
  • All participants must undergo multidisciplinary evaluation by a qualified colorectal surgeon, medical oncologist, and radiation oncologist to discuss treatment options for rectal cancer.
  • Per the treating surgeon, the patient must be a candidate for both TES and/or TME for rectal cancer.
  • Per the treating medical oncologist, the patient must be a candidate for standard chemotherapy for rectal cancer.
  • Per the treating radiation oncologist, the patient must be a candidate for standard radiation/chemoradiotherapy for rectal cancer.
  • The effects of botensilimab with balstilimab on the developing human fetus are unknown. For this reason, women of child-bearing potential (WOCBP) and men enrolled in this study must agree to use highly effective contraceptive measures (See Section 3.4) starting with the Screening Visit through 90 days after the last dose of study treatment. See section 3.4 for more detailed information on contraception requirements.
  • Ability to understand and the willingness to sign a written informed consent document.

Who cannot join

  • Tumor is MSI-H/MMRd per any local testing.
  • Known TMB >20mut/Mb or indication for immune checkpoint inhibitor therapy including hypermutated cancers.
  • Received prior anti-CTLA-4 or anti-PD-1/PD-L1 therapy and/or other experimental immunologic agents.
  • Partial or complete bowel obstruction within the last 3 months, signs/symptoms of bowel obstruction, or known radiologic evidence of impending obstruction.
  • Uncontrolled irritable bowel syndrome with predominant diarrhea (IBS-D) and/or other uncontrolled, chronic diarrhea syndromes.
  • Presence of rectal cancer metastases.
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  • Stigmata of hepatic decompensation including a history of variceal bleeding, a history of ascites related to hepatic cirrhosis, or severe portal hypertension.
  • Clinically significant (i.e., active) cardiovascular disease: cerebral vascular accident/stroke or myocardial infarction within 6 months of enrollment, unstable angina, congestive heart failure (New York Heart Association class ≥ III), or serious uncontrolled cardiac arrhythmia requiring medication.
  • Concurrent malignancy (present during screening) requiring treatment or history of prior malignancy active within 2 years prior to the first dose of study treatment, i.e., patients with a history of prior malignancy are eligible if treatment was completed at least 2 years before the first dose of study treatment and the patient has no evidence of disease. Patients with history of prior early-stage basal/squamous cell skin cancer, low-risk prostate cancer eligible for active surveillance, or noninvasive or in situ cancers who have undergone definitive treatment at any time are also eligible.
  • Treatment with one of the following classes of drugs within the delineated time window prior to C1D1:
  • Cytotoxic, targeted therapy or other investigational therapy within 3 weeks.
  • Investigational monoclonal antibodies, antibody-drug conjugates, radioimmunoconjugates, or similar therapy, within 4 weeks, or 5 half-lives, whichever is shorter.
  • Small molecule/tyrosine kinase inhibitors within 2 weeks or less than 5 circulating half- lives of investigational drug.
  • Prior therapy for rectal cancer.
  • Prior pelvic radiation therapy.
  • Prior treatment for rectal cancer.
  • Known allergy or hypersensitivity to any of the study drugs or any of the study drug excipients.
  • Any evidence of current interstitial lung disease (ILD) or pneumonitis, or prior history of ILD or non-infectious pneumonitis requiring glucocorticoids.
  • History of allogeneic organ transplant.
  • Psychiatric or substance abuse disorders that would interfere with cooperation with the requirements of the study.
  • Patients with a condition requiring systemic treatment with either corticosteroids (> 10 mg daily prednisone equivalent) within 14 days or another immunosuppressive medication within 30 days of the first dose of study treatment. Inhaled or topical steroids, and adrenal replacement steroid doses (≤ 10 mg daily prednisone equivalent) are permitted in the absence of active autoimmune disease.
  • Active autoimmune disease or history of autoimmune disease that required systemic treatment within 2 years of the start of study treatment (i.e., with use of disease-modifying agents or immunosuppressive drugs).
  • History or current evidence of any condition, co-morbidity, therapy, any active infections, or laboratory abnormality that might confound the results of the study, interfere with the patient's participation for the full duration of the study, or is not in the best interest of the patient to participate, in the opinion of the treating Investigator.
  • Uncontrolled infection with HIV and/or active infection with opportunistic pathogens. Patients stable on antiretroviral therapy with undetectable viral load and normal CD4 counts for at least 6 months prior to study entry are eligible. Serological testing for HIV at screening is not required.
  • Known to be positive for HBV surface antigen, or any other positive test for HBV indicating acute or chronic/latent infection. HBV testing is required for study entry.
  • Known active HCV as determined by positive serology and confirmed by polymerase chain reaction (PCR). Patients on or who have received antiretroviral therapy are eligible provided they are virus-free by PCR for at least 6 months prior to study entry.
  • History of untreated TB and/or positive quantiferon/Tspot test without previous tuberculosis prophylaxis, or untreated active infection with Mycobacterium tuberculosis. Testing must be negative for study entry.
  • Active or known prior infection with nontuberculous mycobacteria.

Trial locations and contacts

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

Benjamin Schlechter, MD contact

617-632-4607

benjamin_schlechter@dfci.harvard.edu

United States3 sites, 2 recruiting

  • Brigham and Women's Hospital

    Boston, Massachusetts, 02115

    Danielle Lindquist, 8572152000, DanielleA_Lindquist@DFCI.HARVARD.EDU

    Benjamin L Schlechter, MD

    Recruiting

  • Dana-Farber Cancer Institute

    Boston, Massachusetts, 02115

    Danielle Lindquist, 8572152000, DanielleA_Lindquist@DFCI.HARVARD.EDU

    Benjamin Schlechter, MD

    Recruiting

  • Beth Israel Deaconess Medical Center (BIDMC)

    Boston, Massachusetts, 02215

    Active, not recruiting

Other trials in United States

About this study

Official title: A Phase 2 Study of the Safety and Efficacy of Neoadjuvant Botensilimab in Combination With Balstilimab in the Treatment of Microsatellite Stable / Mismatch Repair Proficient Early Rectal Cancer (RECTIFY-1)

This is a multi-site, prospective, non-randomized phase 2 study evaluating neoadjuvant botensilimab in combination with balstilimab for patients with microsatellite stable (MSS) / mismatch repair proficient (MMRp) early rectal cancer staged T1-T2 N0 by MRI and considered candidates for surgical resection without standard neoadjuvant therapies. Participants will receive a single IV dose of botensilimab on Day 1 followed by balstilimab IV every 2 weeks for up to 6 months, with tumor response assessments during treatment and follow-up afterward.

Read the detailed description

This study is a multi-site, prospective, non-randomized, phase 2 trial. The protocol proposes to treat 16 participants with a single fixed dose of botensilimab 75 mg IV on the first day of treatment, followed by balstilimab 240 mg IV every 2 weeks for up to 6 months. The schema states that patients with stage I MSS/MMRp rectal cancer (T1-2 N0 by MRI) will undergo tumor response assessment during treatment for 6 months. After treatment, participants with complete or near complete response and pathologic complete response at local excision may undergo non-operative management with long-term surveillance, while those with residual disease or tumor progression will undergo management per standard of care. The study calendar includes treatment cycles, discontinuation, 30-day and 90-day safety follow-up, efficacy follow-up, and survival follow-up by phone every 12 weeks.

Being tested
Botensilimab, Balstilimab
Keywords
Early rectal cancer, Non-operative management, Microsatellite Stable Rectal Carcinoma, stage I rectal cancer
Medical subject headings
Rectal Neoplasms

What participants receive

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

  • BotensilimabDrug

    one IV infusion on Cycle 1 Day 1, over about 30 minutes

  • BalstilimabDrug

    IV infusion every 2 weeks on Day 1 of each treatment cycle, over about 30 minutes, for up to 6 months

Study groups in NCT07735624
Study groupRoleWhat they receive
Botensilimab + BalstilimabExperimentalParticipants receive: * Botensilimab: one IV infusion on Cycle 1 Day 1, over about 30 minutes * Balstilimab: IV infusion every 2 weeks on Day 1 of each treatment cycle, over about 30 minutes, for up to 6 months The protocol specifies: * Botensilimab dose: 75 mg IV once * Balstilimab dose: 240 mg IV every 2 weeks for up to 6 months
Receives: Drug: Botensilimab; Drug: Balstilimab

What is being measured

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

  1. Complete response (cCR plus nCR with pCR at resection) within 6 months from initiation of therapy or nCR with pathologic complete response (pCR) with TES

    Tumor response will be evaluated by a qualified colorectal surgeon using flexible sigmoidoscopy (or equivalent), with biopsy as clinically indicated, and rectal MRI using standard response criteria. Response categories are clinical complete response, near-complete clinical response, no response, or progression. Participants with near-complete clinical response must have pathologic complete response at TES/local excision to meet the endpoint.

    Measured: From baseline to 6 months from initiation of therapy

Secondary outcomes (6)

  1. Incidence of treatment-emergent adverse events

    Adverse events will be classified and graded according to NCI CTCAE version 6.0. Toxicity results will be presented descriptively using frequencies and percentages.

    Measured: From first treatment through survival follow-up, up to 5 years from initiation of therapy

  2. Incidence of surgical complications

    Surgical complications will be graded according to the Clavien-Dindo classification among participants who undergo local excision/TES or total mesorectal excision.

    Measured: From surgery through 90-day safety follow-up

  3. Organ preservation rate

    Organ preservation rate is defined as the proportion of participants who avoid total mesorectal excision. Local excision/TES without total mesorectal excision is considered organ preservation.

    Measured: From initiation of therapy through post-treatment surgical management decision, approximately 6 months

  4. 3-year locoregional recurrence rate

    Locoregional recurrence rate is defined as the proportion of participants with local or regional recurrence as the initial site of failure within 3 years from initiation of therapy.

    Measured: From initiation of therapy to 3 years.

  5. Disease-free survival

    Disease-free survival is defined as survival without evidence of local recurrence, distant metastasis, or death from any cause within 3 years from initiation of therapy. Participants alive without disease progression are censored at the date of last disease evaluation.

    Measured: From initiation of therapy to 3 years.

  6. Overall survival

    Overall survival is defined as survival without death from any cause within 5 years from initiation of therapy.

    Measured: From initiation of therapy to 5 years.

Timeline

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

  1. First posted30 Jul 2026
  2. Study start10 Aug 2026
  3. Primary completion1 Jun 2027 (estimated)
  4. Study completion31 Dec 2032 (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
16 participants (estimated)
IDs, dates and publications
ClinicalTrials.gov ID
NCT07735624
Sponsor's protocol ID
26-298
Acronym
RECTIFY-1
Status last verified
Nov 2026
First submitted
24 Jul 2026
Last updated
3 Nov 2026
Results posted
No
Data monitoring committee
Yes
FDA-regulated drug
Yes
FDA-regulated device
No
Individual data sharing
Yes: The Harvard Cancer Consortium encourages and supports the responsible and ethical sharing of data from clinical trials. De-identified participant data from the final research dataset used in the published manuscript may only be shared under the terms of a Data Use Agreement. Requests may be directed to: Benjamin Schlecher. The protocol and statistical analysis plan will be made available on Clinicaltrials.gov only as required by federal regulation or as a condition of awards and agreements supporting the research.

Questions about this trial

What is this clinical trial studying?

A Phase 2 study testing Botensilimab and Balstilimab in people with Early Rectal Cancer and Stage I Rectal Cancer, run by Dana-Farber Cancer Institute at 3 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 20 inclusion and 28 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 3 Nov 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 3 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 Benjamin Schlechter, MD (617-632-4607, benjamin_schlechter@dfci.harvard.edu), or a site near the patient. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Complete response (cCR plus nCR with pCR at resection) within 6 months from initiation of therapy or nCR with pathologic complete response (pCR) with TES (time frame: From baseline to 6 months from initiation of therapy). 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 NCT07735624.

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 3 Nov 2026.

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