On December 7, 2019 Fate Therapeutics, Inc. (NASDAQ: FATE), a clinical-stage biopharmaceutical company dedicated to the development of programmed cellular immunotherapies for cancer and immune disorders, reported that initial clinical data for its FT516 and FT500 off-the-shelf, iPSC-derived natural killer (NK) cell product candidates (Press release, Fate Therapeutics, DEC 7, 2019, View Source [SID1234552027]).

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"The safety, tolerability, and immunogenicity data from the Phase 1 dose-escalation stage of FT500, the first-ever cell therapy derived from a clonal master induced pluripotent stem cell line to undergo clinical investigation in the U.S., provide compelling evidence that multiple doses of iPSC-derived NK cells can be delivered off-the-shelf and administered without patient matching," said Wayne Chu, M.D., Vice President of Clinical Development of Fate Therapeutics. "Additionally, initial clinical observations with FT516 are very encouraging, as an assessment of the first AML patient’s bone marrow at Day 42 following three once-weekly doses of FT516 demonstrated anti-leukemia activity and hematopoietic recovery."

FT516 Universal, Off-the-shelf, Engineered iPSC-derived NK Cell Product Candidate
The FT516 study is an open-label, multi-dose Phase 1 clinical trial as a monotherapy for the treatment of acute myeloid leukemia (AML) and in combination with CD20-directed monoclonal antibodies for the treatment of advanced B-cell lymphoma, and is the first-ever clinical investigation of a cell product derived from a clonal master engineered induced pluripotent stem cell (iPSC) line. Two patients, both heavily pretreated, have been treated with FT516 to date, and the first clinical findings include:

FT516 First AML Patient. The first patient enrolled for the treatment of AML was refractory to initial 7+3 induction therapy, multiple subsequent re-induction attempts with chemotherapy, and a combination therapy of venetoclax plus decitabine. Following outpatient lympho-conditioning, the patient received a first cycle of three once-weekly doses of FT516 (90 million cells per dose) as a monotherapy and IL-2 cytokine support. A bone marrow biopsy obtained at Day 42 following the completion of the first FT516 treatment cycle showed no morphologic evidence of leukemia and evidence of hematopoietic recovery. Concurrently, no circulating leukemia cells were observed in the peripheral blood, and the patient showed neutrophil recovery without growth factor support (>1,000 per µL). In addition, no dose-limiting toxicities (DLTs), Grade ≥3 adverse events (AEs) or serious adverse events (SAEs) related to FT516 were reported. The patient is expected to receive a second FT516 treatment cycle of three once-weekly doses of FT516. A formal response assessment will be performed following completion of this second FT516 treatment cycle.
FT516 First Lymphoma Patient. Prior to treatment with FT516, the first patient enrolled with high-risk diffuse large B-cell lymphoma (DLBCL) having relapsed after multiple rituximab combination regimens, autologous hematopoietic stem cell transplant, and chimeric antigen receptor (CAR) T-cell therapy. Following outpatient lympho-conditioning, the patient received a first cycle of three once-weekly doses of FT516 (30 million cells per dose) in combination with rituximab and IL-2 cytokine support. A second treatment cycle of three once-weekly doses of FT516 in combination with rituximab has been initiated. A formal response assessment will be performed following completion of this second FT516 treatment cycle.
FT500 Universal, Off-the-shelf, iPSC-derived NK Cell Product Candidate
FT500 is the first iPSC-derived cell product candidate to emerge from the Company’s iPSC product platform. The FT500 study is an open-label, multi-dose Phase 1 clinical trial for the treatment of advanced solid tumors. The dose-escalation stage of the study is designed to assess the safety and tolerability of three once-weekly doses of FT500, without IL-2 cytokine support, as a monotherapy and in combination with one of three FDA-approved immune checkpoint inhibitor (ICI) therapies in patients that have failed prior ICI therapy.

As of a November 28, 2019 data cutoff, 12 patients (n=8 monotherapy; n=4 in combination with ICI) have been treated with FT500, and the key clinical findings include:

Safety. No DLTs, FT500-related SAEs or FT500-related Grade ≥3 AEs, and no incidents of cytokine release syndrome, neurotoxicity, or graft-versus-host disease, have been reported in 12 patients.
Tolerability. All 12 patients completed the first FT500 treatment cycle of three once-weekly doses. Nine of 11 patients initiated a second FT500 treatment cycle, with eight of nine patients having completed the second FT500 treatment cycle. One patient is currently pending initiation of a second FT500 treatment cycle. The multi-dose, two-cycle treatment schedule was well-tolerated, and no treatment discontinuations were due to AEs.
Anti-FT500 T-cell Mediated Immunogenicity. The T-cell compartment of nine patients was evaluated for T-cell mediated host-versus-product allo-reactivity. A TCR repertoire analysis conducted at multiple time points following treatment with FT500 demonstrated that a maximum of up to 6% of the T-cell clones in the patients’ reconstituted T-cell compartment were comprised of pre-existing low-frequency T-cell clones, suggesting that a robust T-cell response against FT500 was not evident. As a point of contrast, in subjects undergoing immunization for infectious disease, it is observed that almost 90% of the T-cell clones that emerge existed in low frequency prior to immunization.
Anti-FT500 B-cell Mediated Immunogenicity. The antibody repertoire of 11 patients was analyzed for targeting of the six HLA class I types expressed by FT500 to assess B-cell mediated host-versus-product allo-reactivity. Among the 11 patients, a single FT500 anti-HLA antibody with a mean fluorescence intensity (MFI) level of ≥ 5,000 was detected in a single patient, suggesting that a robust anti-FT500 B-cell response was not evident. As a point of reference, in patients undergoing haplo-identical hematopoietic stem cell transplant, an MFI level ≥ 5,000 has been correlated with a 5-fold increase in risk of graft rejection.
FT500 Anti-tumor Activity. In the monotherapy arm, two of three patients in the 100 million cells per dose cohort and two of five patients in the 300 million cells per dose cohort achieved a best overall response of stable disease per iRECIST. In the ICI combination arm, two of three patients in the 100 million cells per dose cohort achieved a best overall response of stable disease per iRECIST. A fourth patient in the ICI combination arm is currently undergoing treatment in the 300 million cells per dose cohort.
Upon successful completion of the 300 million cells per dose cohort in the ICI combination arm, the Company plans to amend the current FT500 clinical protocol to include IL-2 cytokine support with each dose of FT500 and enrich for cancers that are expected to be amenable to NK cell anti-tumor activity. In the dose-expansion stage of the FT500 Phase 1 study, FT500 will be administered at 300 million cells per dose in combination with ICI therapy under this revised clinical protocol.