Tumor-reactive clonotype dynamics underlying clinical response to TIL therapy in melanoma

The profiles, specificity and dynamics of tumor-specific clonotypes that are associated with clinical response to adoptive cell therapy (ACT) using tumor-infiltrating lymphocytes (TILs) remain unclear. Using single-cell RNA/TCR-sequencing, we tracked TIL clonotypes from baseline tumors to ACT products and post-ACT blood and tumor samples in melanoma patients treated with TIL-ACT. Patients with clinical responses had baseline tumors enriched in tumor-reactive TILs, which were more effectively mobilized upon in vitro expansion, yielding products with higher numbers of tumor-specific CD8+ cells, which also preferentially infiltrated tumors post-ACT. Conversely, lack of clinical responses was associated with tumors devoid of tumor-reactive resident clonotypes, and with cell products mostly composed of blood-borne clonotypes mainly persisting in blood but not in tumors post-ACT. Upon expansion, tumor-specific TILs lost the specific signatures of states originally exhibited in tumors, including exhaustion, and in responders acquired an intermediate exhausted effector state after tumor engraftment, revealing important functional cell reinvigoration. ### Competing Interest Statement GC has received grants, research support or has been coinvestigator in clinical trials by Bristol-Myers Squibb, Tigen Pharma, Iovance, F. Hoffmann-La Roche AG, Boehringer Ingelheim. The Lausanne University Hospital (CHUV) has received honoraria for advisory services G. Coukos has provided to Genentech, AstraZeneca AG, EVIR. GC has previously received royalties from the University of Pennsylvania for CAR-T cell therapy licensed to Novartis and Tmunity Therapeutics. DDL, SB, AH, and GC are inventors on patent applications filed by the Ludwig Institute for Cancer Research Ltd on behalf also of the University of Lausanne and the CHUV pertaining to the subject matter disclosed herein and such patent applications have been licensed to Tigen Pharma SA. SZ is currently an employee of F. Hoffmann-La Roche. OM has consulting/advisory roles for Bristol Myers Squibb, MSD, Roche, Novartis, Amgen, Pierre Fabre, Neracare; research grants from Bristol Myers Squibb, MSD, Amgen. PCL; consultant advisor or paid speaker for Bristol Myers Squibb, MSD, Novartis, Pierre Fabre, Amgen, Nektar; has received research funding from Bristol Myers Squibb, Pierre Fabre. All the other authors have no conflict of interest to declare.