long term outcomes of pediatric patients with malignant and non malignant disorders receiving α β t cell depleted hla haploidentical hematopoietic stem cell transplantation hsct followed by infusion of bpx 501 t cells donor t cells transduced with ic9

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Multicenter, Open-Label, Phase 3 Study of Tabelecleucel for Solid Organ or Allogeneic Hematopoietic Cell Transplant Recipients with Epstein-Barr Virus-Driven Post Transplant Lymphoproliferative Disease after Failure of Rituximab or Rituximab and Chemotherapy (ALLELE)

Abstract Background: Tabelecleucel is an investigational, off-the-shelf, allogeneic Epstein-Barr virus (EBV)-specific T-cell immunotherapy being studied in patients (pts) with serious EBV-driven diseases, including post-transplant lymphoproliferative disease (EBV + PTLD). The median overall survival (OS) after treatment failure of rituximab is short at ~1.7 months in EBV + PTLD following hematopoietic cell transplant (HCT) (Socié EBMT 2020) and ~3 months in solid organ transplant (SOT) recipients with EBV + PTLD whose disease relapsed after rituximab and who did not respond to or did not receive chemotherapy (CT) (Zimmerman EHA 2019). These poor outcomes demonstrate an urgent unmet need for effective therapies in this ultra-rare serious disease. Promising outcomes have previously been demonstrated (Prockop JCI 2020). Additionally, we have shown clinical benefit with a >60% objective response rate (ORR) and >80% estimated 2-year OS rates (Prockop EBMT 2021, Prockop ATC 2021) in pts with EBV + PTLD, irrespective of pts achieving a complete response (CR) or partial response (PR) to tabelecleucel. Safety data have been assessed in >150 pts with EBV + PTLD treated with tabelecleucel with tumor flare reaction (TFR) as the only identified risk. Here, for the first time, we report interim efficacy and safety results from the pivotal phase 3 clinical trial ALLELE (NCT03394365) - a multicenter, open-label study of tabelecleucel after failure of rituximab ± CT in pts with EBV + PTLD following SOT or HCT. Methods: ALLELE is evaluating the clinical benefit of tabelecleucel in two cohorts: (1) pts with EBV + PTLD following SOT after failure of rituximab ± CT (n=33), and (2) pts with EBV + PTLD following HCT after failure of rituximab monotherapy (n=33). Tabelecleucel is administered at a dose of 2 x 10 6 cells/kg on days 1, 8, and 15, followed by observation through each cycle lasting 35 days. Response per clinical and radiographic assessment (by PET/CT) is evaluated by the investigator and by independent review using Lugano Classification with LYRIC modification. Key efficacy endpoints include ORR, duration of response (DOR), time to response (TTR), and OS. After treatment is completed or discontinued, pts are assessed every 3 months up to 24 months, and every 6 months thereafter for survival status up to 5 years. Results: As of May 2021, 38 pts (24 SOT, 14 HCT) were evaluable for response assessment by independent oncologic response adjudication (IORA) and had the opportunity for 6 months follow-up (Table 1). SOT and HCT pts received a median (range) of 2.0 (1-6) and 3.0 (1-5) cycles of tabelecleucel, respectively. ORR was 50% (19/38, 95% CI: 33.4, 66.6) in the overall population, 50.0% (12/24, 95% CI: 29.1, 70.9) in SOT, and 50.0% (7/14, 95% CI: 23.0, 77.0) in HCT, with a best overall response of CR (n=5, SOT; n=5, HCT) or PR (n=7, SOT; n=2, HCT; Table 2). Overall, median TTR was 1.1 months (0.7-4.7), 11 of 19 responders had a DOR lasting >6 months, and median DOR was not reached (Table 2). Median OS was 18.4 (95% CI: 6.9, NE) months overall, 16.4 (95% CI: 3.5, NE) months for SOT, and not yet reached for HCT. 1-year survival rate was 61.1% (95% CI: 42.9, 75.0) overall, 57.4% (95% CI: 35.2, 74.5) for SOT, and 66.8% (95% CI: 32.4, 86.6) for HCT. Those who responded had a longer survival compared to the non-responders, with a median OS of NE (95% CI: 16.4, NE) and 1-year survival rate of 89.2% (95% CI: 63.1, 97.2). Non-responders had a median OS of 5.7 (95% CI: 1.8, 12.1) months and 1-year survival rate of 32.4% (95% CI: 12.1, 54.9) (Table 3). Serious treatment emergent AEs (TEAEs) were reported in 62.5% of SOT and 57.1% of HCT pts. Fatal TEAEs were reported in 16.7% of SOT and 7.1% of HCT pts; none of the fatal TEAEs were related to study treatment. Tabelecleucel was well-tolerated with no reports of TFR and no confirmed evidence for graft vs host disease, organ rejection, infusion reactions, or cytokine release syndrome in relation to tabelecleucel in these treatment refractory and immunocompromised pts. Conclusions: Tabelecleucel phase 3 interim data are reported here for the first time and show clinically meaningful outcomes and promising ORR and OS in a pt population with no approved treatment options and otherwise poor survival. Tabelecleucel, an allogeneic cell therapy, was well tolerated without evidence of safety concerns typically observed with autologous chimeric antigen receptor cell therapies. Figure 1 Figure 1. Disclosures Prockop: Memorial Sloan Kettering Cancer Center: Other: S Prockop receives support for the conduct of sponsored clinical trials through MSK from Atara Biotherapeutics, Jasper and AlloVir. , Patents & Royalties: S Prockop is a co-inventor on intellectual property (IP) licensed to Atara. S Prockop has waived rights to this IP to MSK and has no personal financial interests in Atara. MSK has financial interests in Atara and IP interests relevant to this abstract. ; Atara Biotherapeutics: Other: support for the conduct of sponsored trials and Inventor; Jasper: Other: support for the conduct of sponsored trials; AlloVir: Other: support for the conduct of sponsored trials; Neovii: Consultancy; ADMA Biologics: Consultancy; MSK: Other: Inventor. Mahadeo: Atara Biotherapeutics: Consultancy. Beitinjaneh: Kite/Gilead: Other: Ad Board Event Attendee. Choquet: Sanofi, Celegene, Roche, Abbvie, Sandoz, Janssen, Takeda: Consultancy. Stiff: Cellectar: Research Funding; CRISPR: Consultancy; Gamida-Cell, Atara, Amgen, Incyte, Takeda, Macrogenetics, Eisai: Research Funding. Reshef: Bayer, BMS, Regeneron, TScan, Synthekine, Atara, Jasper: Consultancy. Dahiya: Kite, a Gilead Company: Consultancy; Miltenyi Biotech: Research Funding; Atara Biotherapeutics: Consultancy; Jazz Pharmaceuticals: Research Funding; BMS: Consultancy. Parmar: Atara Biotherapeutics: Current Employment. Ye: Atara Biotherapeutics: Current Employment. Gamelin: Atara Biotherapeutics: Current Employment. Dinavahi: Atara Biotherapeutics: Current Employment

Properties of the Arg376 residue of the proton-coupled folate transporter (PCFT-SLC46A1) and a glutamine mutant causing hereditary folate malabsorption

The proton-coupled folate transporter (PCFT-SLC46A1) is required for intestinal folate absorption and is mutated in the autosomal recessive disorder, hereditary folate malabsorption (HFM). This report characterizes properties and requirements of the R376 residue in PCFT function, including a R376Q mutant associated with HFM. Gln, Cys, and Ala substitutions resulted in markedly impaired transport of 5-formyltetrahydrofolate (5-FTHF) and 5-methyltetrahydrofolate (5-MTHF) due to an increase in Km and decrease in Vmax in HeLa R1–11 transfectants lacking endogenous folate transport function. In contrast, although the influx Km for pemetrexed was increased, transport was fully preserved at saturating concentrations and enhanced for the like-charged R376K- and R376H-PCFT. Pemetrexed and 5-FTHF influx mediated by R376Q-PCFT was markedly decreased at pH 5.5 compared with wild-type PCFT. However, while pemetrexed transport was substantially preserved at low pH (4.5–5.0), 5-FTHF transport remained very low. Electrophysiological studies in Xenopus oocytes demonstrated that 1) the R376Q mutant, like wild-type PCFT, transports protons in the absence of folate substrate, and in this respect has channel-like properties; and 2) the influx Km mediated by R376Q-PCFT is increased for 5-MTHF, 5-FTHF, and pemetrexed. The data suggest that mutation of the R376 residue to Gln impairs proton binding which, in turn, modulates the folate-binding pocket and depresses the rate of conformational alteration of the carrier, a change that appears to be, in part, substrate dependent

High-Risk Acute Myeloid Leukemia: A Pediatric Prospective

Pediatric acute myeloid leukemia is a clonal disorder characterized by malignant transformation of the hematopoietic stem cell. The incidence and the outcome remain inferior when compared to pediatric ALL, although prognosis has improved in the last decades, with 80% overall survival rate reported in some studies. The standard therapeutic approach is a combined cytarabine and anthracycline-based regimen followed by consolidation with allogeneic stem cell transplantation (allo-SCT) for high-risk AML and allo-SCT for non-high-risk patients only in second complete remission after relapse. In the last decade, several drugs have been used in clinical trials to improve outcomes in pediatric AML treatment