The FDA has granted fast-track designation to the nonengineered autologous cellular immunotherapy suplexa for the treatment of patients with microsatellite instability–high (MSI-H) colorectal cancer (CRC).1
This regulatory decision was supported by results from the phase 1, first-in-human SUPLEXA-101 study (NCT05237206). Final efficacy and safety data from the study, which were shared at the 39th Annual Society for Immunotherapy of Cancer Meeting, showed signals of antitumor activity with suplexa across patients with solid tumors (n = 35), most notably in MSI-H CRC.2 Within this group, 3 patients achieved a complete response (CR), a partial response (PR), and stable disease (SD), respectively. An additional PR was observed in the clear cell renal cell carcinoma group. Notably, responses among the patients who achieved CR and PR extended beyond 80 weeks. Overall, 18 additional patients in the overall patient population achieved SD, and 10 patients total experienced disease progression.
All prespecified study end points were achieved. Across all solid tumors, the 12- and 24-week event-free survival (EFS) rates were 61.2% (95% CI, 41.8%-75.1%) and 36.9% (95% CI, 19.3%-50.6%), respectively; the 36- and 48-week EFS rates for both were 32.8% (95% CI, 16.1%-50.6%).
Regarding safety, no dose-limiting toxicities, treatment-related serious adverse effects (AEs) or injection-site reactions were reported in the overall study population; moreover, treatment-emergent AEs were mild and self-limiting. Safety was established across a wide dose range of 3 to 20 doses of 2.5 billion cells per patient.
"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 a news release.1 "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.”
Suplexa Nets FDA Fast Track Designation in MSI-H CRC
- The FDA has awarded fast-track designation to Suplexa, a nongenetically modified autologous cellular therapy, for treating patients with MSI-high CRC.
- In the first-in-human SUPLEXA-101 trial of 35 patients with solid tumors, Suplexa achieved its primary end points, showing a favorable safety profile and robust, long-lasting clinical activity—with responses lasting over 80 weeks in the MSI-H CRC cohort.
- Driven by these encouraging clinical and safety outcomes, a phase 2 open-label trial will evaluate Suplexa combined with checkpoint inhibitors as a first-line treatment for mismatch repair–deficient, MSI-H CRC.
What is the mechanism of action of suplexa?
Suplexa is derived from a patient's own peripheral blood mononuclear cells.2 These highly activated immune cells express features that enable direct tumor lysis, as well as traits of antigen-presenting cells, and are broadly cytolytic against several tumor cell lines without harming normal cells.
The regimen leverages Alloplex's proprietary ENLIST platform to train and activate immune cells without genetic modification.1 By avoiding genetic engineering, this manufacturing method is designed to be highly scalable and reproducible, directly overcoming a major logistical hurdle that has historically limited the widespread use of oncology cell therapies.
What was the design of SUPLEXA-101?
SUPLEXA-101 evaluated the safety, tolerability, and preliminary efficacy of repeated intravenous (IV) infusions of suplexa monotherapy in patients with measurable metastatic solid tumors (cohort 1) and hematologic malignancies (cohort 2).3
Eligible patients received a minimum cumulative dose of 7.5 × 10⁹ suplexa therapeutic cells, administered as repeated intravenous infusions.2 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.
The primary end point was to characterize the safety and tolerability of suplexa. In cohort 1, efficacy was a secondary end point.1
The clinical and mechanistic findings from SUPLEXA-101 support the initiation of an open-label phase 2 trial evaluating suplexa in combination with checkpoint inhibitors vs checkpoint inhibitors alone in the front line for patients with mismatch repair–deficient, MSI-high CRC.2
References
- Alloplex Biotherapeutics. Alloplex Biotherapeutics receives FDA fast track designation for SUPLEXA in colorectal cancer indication. News release. Alloplex Biotherapeutics. May 13, 2026. Accessed May 19, 2026. https://alloplexbio.com/alloplex-biotherapeutics-receives-fda-fast-track-designation-for-suplexa-in-colorectal-cancer-indication/
- Joshi R, Goh J, G Kichenadasse, et al. Final safety and efficacy update of SUPLEXA-101, a first-in-human, single-agent study of SUPLEXA therapeutic cells in metastatic solid tumors. J Immunother Cancer. 2024;12(suppl 2):0608. doi:10.1136/jitc-2024-SITC2024.0608
- 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. Updated September 18, 2025. Accessed May 19, 2026. https://clinicaltrials.gov/study/NCT05237206
