FDA Grants Fast Track Designation to Suplexa for MSI-H Colorectal Cancer

The FDA has granted a fast track designation to suplexa for the treatment of patients with microsatellite instability–high (MSI-H) colorectal cancer, according to Alloplex Biotherapeutics, the company developing the non-engineered autologous cellular immunotherapy.¹

The fast track designation was supported by results from the SUPLEXA-101 study (NCT05237206),² a completed first-in-human phase 1 basket trial conducted at multiple sites in Australia. Among the findings that led to the designation were responses occurring in 2 patients with MSI-H colorectal cancer treated with suplexa monotherapy. One patient had a complete response and the other had a partial response, and both patients maintained durable responses exceeding 80 weeks.³

The cellular therapy suplexa is derived from a patient's own peripheral blood mononuclear cells and is prepared using Alloplex's proprietary ENLIST immune cell training platform, which activates immune cells without any genetic modification. According to Alloplex, the manufacturing approach is intentionally designed to be more scalable and reproducible than genetically engineered alternatives, addressing a longstanding practical barrier to the wider adoption of cellular therapies in oncology.

"This designation represents a pivotal regulatory milestone for suplexa and validates our platform's potential to transform solid tumor oncology," Frank Borriello, MD, PhD scientific founder and chief executive officer of Alloplex, stated in the news release. "By moving beyond the limitations of genetic engineering, we are pursuing a more natural, yet more powerful, way to harness the immune system. We look forward to working closely with the FDA as we transition into the clinic to bring this new class of therapy to patients who have exhausted standard options," added Borriello.

SUPLEXA-101 Trial

The phase 1 SUPLEXA-101 trial enrolled up to 40 patients with metastatic cancers across 2 cohorts. One cohort comprised solid tumor patients with histologically, cytologically, or radiographically confirmed disease, and the second enrolled patients with hematologic malignancies including multiple myeloma, lymphoma, and chronic lymphocytic leukemia. All participants had exhausted standard-of-care treatment options before entering the trial. The primary objective was to characterize the safety and tolerability of suplexa, with efficacy as a secondary end point.

Enrolled patients received a minimum cumulative dose of 7.5 × 10⁹ suplexa therapeutic cells, administered as repeated intravenous infusions. The minimum dosing regimen consisted of 2.5 billion cells per dose for at least 3 weekly treatments, with continued dosing dependent on manufacturing yield.

Among the 22 patients with available clinical measurements at the time of efficacy analysis, more than 70% achieved stable disease or better by RECIST criteria, with a mean response duration of approximately 19 weeks and a range extending to 35 weeks post-treatment.³ Tumor types represented in the trial included renal cell carcinoma, colorectal cancer, triple-negative breast cancer, lung cancer, melanoma, ovarian cancer, liver cancer, and others. In the renal cell carcinoma subgroup, 60% of patients achieved stable disease.³

Next Steps

The fast track designation confers several practical advantages for Alloplex's development program, including more frequent interactions with the FDA to shape the clinical development strategy, rolling review of regulatory submission components as they are completed.

REFERENCES

1. Alloplex Biotherapeutics. Alloplex Biotherapeutics receives FDA Fast Track Designation for SUPLEXA in colorectal cancer indication. News release. May 13, 2026. https://tinyurl.com/ytxz28n7

2. Alloplex Biotherapeutics. A Phase 1, First-in-Human, Open-Label Single Agent Study of SUPLEXA Therapeutic Cells in Patients With Metastatic Solid Tumours and Haematologic Malignancies (SUPLEXA-101). ClinicalTrials.gov identifier: NCT05237206. Updated September 18, 2025. https://clinicaltrials.gov/study/NCT05237206

3. Joshi R, Goh J, Gargosky S, et al. 727 Topline safety and efficacy update of SUPLEXA-101, a first-in-human, single agent study of SUPLEXA therapeutic cells in 28 patients with metastatic solid tumours. J Immunother Cancer. 2023;11(suppl 1):A822. doi:10.1136/jitc-2023-SITC2023.0727