STIMULUS MDS-US : Sabatolimab Added to HMA in Higher Risk MDS

Single-arm, Open Label, Phase II Study of MBG453 (Sabatolimab) Added to FDA Approved Hypomethylating Agents of Investigator's Choice (IV/SC/Oral) for Patients With Intermediate, High or Very High Risk Myelodysplastic Syndrome (MDS) as Per IPSS-R Criteria (US Multi-center) (STIMULUS MDS-US)

The main objective of this study was to assess the safety profile of MBG453 (sabatolimab) in combination with FDA approved hypomethylating agents (HMAs) of investigator's choice (IV Decitabine or Azacitidine /SC Azacitidine /Oral Decitabine (cedazuridine combination (INQOVI))).

This was a single arm, nonrandomized, open label, Phase II multicenter study of i.v sabatolimab added to FDA approved HMA agents of Investigator's choice (i.v/s.c/oral) in adult patients with intermediate, high or very high risk MDS as per IPSS-R criteria.

There were 4 separate periods of this study:

1. Screening period (signing of written informed consent through day of enrollment),
2. Core phase for up to 12 months,
3. Extension phase for efficacy and/or survival status (up to 12 months after the core phase),
4. Post-treatment safety follow-up period monitoring for AEs for 30 days following the last dose of azacitidine or decitabine or INQOVI (oral decitabine), or 150 days following the last dose of sabatolimab, whichever was later.

During the conduct of the study there were 2 updates to the Novartis development strategy for sabatolimab. Based on the results from the Phase II STIMULUS MDS-1 study, recruitment was halted for CMBG453B1US01 (STIMULUS MDS-US) on 30-Sep-2022. Novartis confirmed the decision to halt recruitment was not based on any safety findings or safety concerns. Patients who were on study treatment or in follow-up were continued as per the protocol. Furthermore, on 11-Jan-2024, all sabatolimab investigators were notified by Novartis that, based on decision taken in Dec-2023, that the sabatolimab development program (which included study CMBG453B1US01) would be terminated. After the decision was made to discontinue the sabatolimab development program, participants already enrolled in the CMBG453B1US01 study were prepared for closure; these close out activities took approximately 9 months. The actual last patient last visit date was 1 Sep 2024.

Key inclusion criteria:

1. Signed informed consent was obtained prior to participation in the study.

2. Age ≥ 18 years at the date of signing the informed consent form (ICF).

3. Morphologically confirmed diagnosis of a myelodysplastic syndrome (MDS) primary or secondary based on 2016 WHO classification by Investigator assessment with one of the following prognostic risk categories, based on the International Prognostic Scoring System (IPSS-R).. Note: MDS diagnosis history were recorded in the CRF:

   • Very high (> 6 points)
   • High (> 4.5 to ≤ 6 points)
   • Intermediate (> 3 to ≤ 4.5 points)

4. Not suitable at the time of Screening for immediate myeloablative/chemotherapy or HSCT based on Investigator assessment of age, comorbidities, local guidelines, institutional practice (any or all of these).

5. Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1 or 2.

6. AST and ALT ≤ 3 × upper limit of normal (ULN).

7. Total bilirubin ≤ 2 × ULN (except in the setting of isolated Gilbert syndrome).

8. Estimated glomerular filtration rate ≥ 30 mL/min/1.73 m2 (estimation based on modification of diet in renal disease formula, by local laboratory).

9. Patient was able to communicate with the Investigator and had the ability to comply with the requirements of the study procedures.

Key exclusion criteria

1. Prior exposure to TIM-3 directed therapy at any time. Prior therapy with immune checkpoint inhibitors (e.g., anti-CTLA4, anti-PD-1, anti-PD-L1, or anti-PD-L2), cancer vaccines were allowed only if the last dose of the drug was administered more than 4 months prior to enrollment.

2. Previous treatment for intermediate, high or very high risk MDS (based on IPSS-R) with chemotherapy or other antineoplastic agents including lenalidomide and hypomethylating agent (HMAs) such as decitabine or INQOVI (oral decitabine) or azacitidine (patients who had up to 1 cycle of HMAs were included). However, previous treatment with hydroxyurea was permitted.

3. Diagnosis of acute myeloid leukemia (AML) including acute promyelocytic leukemia and extra-medullary acute myeloid leukemia based on WHO 2016 classification.

4. Diagnosis of Chronic myelomonocytic leukemia (CMML), or primary or secondary myelofibrosis based on 2016 WHO classification.

5. History of organ transplant or allogenic HSCT.

6. Patients with prior malignancy, except:

   1. Patients with history of lower risk Myelodysplastic syndrome (MDS) treated by supportive care (e.g., growth factors, transforming growth factor- beta agents) or untreated were eligible.
   2. Patients with history of lower risk MDS who were treated adequately with lenalidomide and then failed were eligible.
   3. Patients with history of adequately treated malignancy for which no anticancer systemic therapy (namely chemotherapy, radiotherapy or surgery) was ongoing or required during the course of the study. Patients who were receiving adjuvant therapy such as hormone therapy were eligible.

7. Patients with MDS based on 2016 WHO classification with revised International Prognostic Scoring System (IPSS-R) ≤ 3.