Relapse kills roughly 38% of AML patients who reach allogeneic hematopoietic cell transplantation, and it does so despite transplant representing the most aggressive curative option available. That baseline is why the Cohort C numbers from TScan’s ALLOHA Phase 1 study deserve attention: 11 of 14 patients who received their first infusion of TSC-101 achieved complete donor chimerism within approximately three weeks, and all five patients assessed after a second infusion hit the same mark. The therapy is designed to eliminate residual recipient hematopoietic cells post-transplant, essentially closing the biological window through which relapse enters.
The Cohort C data carry a specific structural weight that earlier cohorts did not. This cohort was the first to use TSC-101 manufactured via the commercial-ready process, and the 90% manufacturing success rate across 19 enrolled patients suggests that process translates to the clinic without meaningful degradation. TScan also notes that Cohort C enrolled a higher-risk patient population than Cohort A, which makes the 93% response rate (defined as decreasing recipient chimerism) more striking rather than less. One patient with TP53-mutated AML, a genotype associated with particularly poor post-transplant outcomes, remained in complete donor chimerism six months after transplant. Safety remained consistent with the prior cohort, with adverse events largely attributable to the post-HCT context rather than the therapy itself.
The clinical measurement tool here also matters. TScan used the Alloheme NGS assay, a high-sensitivity platform with a 0.2% detection cutoff that CareDx validated in February 2026 across 198 subjects with 85% sensitivity for relapse detection. Using an assay with that resolution tightens the clinical signal considerably; chimerism results measured at lower sensitivity could easily misclassify borderline responders. The choice of assay is a design decision that will matter when Phase 3 data go to regulators.
TScan says it remains on track to enroll the first patient in the pivotal ALLOHA-2 Phase 3 study this month. The transition from a 19-patient Phase 1 cohort to a registrational trial is where the manufacturing process will face its real test at scale. The single number to track from here is the Phase 3 manufacturing success rate: if it holds near the 90% seen in Cohort C, the commercial viability argument becomes difficult to contest; if it erodes, the entire program’s timeline compresses with it.
Jon Napitupulu is Director of Media Relations at The Clinical Trial Vanguard. Jon, a computer data scientist, focuses on the latest clinical trial industry news and trends.
