Talaris Therapeutics, Inc. presented new data characterizing the mechanisms of FCR001-induced immune tolerance in two oral presentations at the 2022 American Society of Nephrology (ASN) Annual Meeting. The first presentation reported on transcriptional changes following successful tolerization with FCR001. Urinary cell mRNA profiling was conducted on 19 patients tolerized with FCR001 in the Company's Phase 2 clinical trial and 159 control patients who received a living donor kidney transplant (LDKT) but were not treated with FCR001.

The analysis identified a unique urinary cell mRNA signature that is consistent with immune quiescence as defined by the ratio of CTLA-4 to granzyme B mRNA, which is significantly higher in the FCR001 cohorts compared to the control cohorts. This signature may help identify FCR001 patients who could safely discontinue chronic immunosuppression. In a second oral presentation, the Company reported data on the specific composition of patients' peripheral blood mononuclear cells (PBMCs) following treatment with FCR001 in a small cohort of patients enrolled in the Company's Phase 3 FREEDOM-1 trial.

Longitudinal single-cell RNA sequencing was conducted on PBMCs from three patients treated with FCR001 and one patient in the standard of care control arm treated with immunosuppressants. The analysis found that immune reconstitution following FCR001 treatment was characterized by important changes in natural killer (NK) cell and B cell sub-populations, and that this immune activation preceded observation of clinical manifestations.