On December 8, 2025 Autolus Therapeutics plc (Nasdaq: AUTL), an early commercial-stage biopharmaceutical company developing, manufacturing and delivering next-generation programmed T cell therapies, reported presentation of preliminary data from the CATULUS Phase 1 trial of obe-cel in pediatric relapsed or refractory (r/r) B-ALL patients, as well as further insights from the registrational FELIX study in adult r/r B-ALL, at the American Society of Hematology (ASH) (Free ASH Whitepaper) Annual Meeting.

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Dr. Matthias Will, Chief Development Officer of Autolus, said: "Pediatric patients with r/r B-ALL have a poor prognosis, particularly those who relapse early. We were pleased to share the first data from the Phase 1 CATULUS trial showing obe-cel can produce high remission rates in this pediatric patient population, including in patients with high-risk relapse and patients with primary CNS relapse. Consistent with our experience in the adult population, data show low rates of severe CRS and ICANS. We are now advancing into the Phase 2 portion of the study in line with our commitment to address the significant unmet need for new treatment options for pediatric patients with r/r ALL."

Dr. Will continued, "Insights from post-hoc analyses from our FELIX pivotal trial in r/r adult B-ALL explored various factors that may help to predict long-term patient outcomes. Specifically, investigators showed that detection of obe-cel in the blood three months post-treatment may be a predictor for long-term outcomes. They also identified characteristics of the product’s cell phenotype as additional factors for treatment outcomes."

He concluded, "In addition to Autolus’ presentations, we were highly encouraged by data from the real-world experience of the ROCCA consortium evaluating CAR T therapy for r/r adult ALL patients. These real world data mirror obe-cel’s safety profile observed in the pivotal FELIX trial with low single digits rates of CRS and ICANS as one of the differentiating characteristics of the therapy."

Abstract 740 – Poster presentation
Title: Treatment of pediatric patients (pts) with relapsed/refractory B-cell acute lymphoblastic leukemia (R/R B-ALL) with obecabtagene autoleucel (obe-cel), a CD19-directed chimeric antigen receptor (CAR) T-cell therapy: preliminary findings from the Phase Ib/II CATULUS trial
Session Name: Acute Lymphoblastic Leukemias: Therapies Excluding Allogeneic Transplantation: Poster II
Session Date and Time: December 7, 2025; 6:00 – 8:00pm ET
Session Room: Orange County Convention Center; West Halls B3-B4
Publication Number: 3337
Presenting Author: Sara Ghorashian, Consultant Haematologist at Great Ormand Street Hospital for Children (GOSH) and Honorary Associate Professor at UCL

Summary: CATULUS is a single-arm, open-label, multi-center study enrolling high-risk patients under age 18 with r/r B-ALL that is primary refractory, in high-risk first relapse, or in second or later relapse. The safety profile of obe-cel in pediatric patients was consistent with that previously reported in adults, with low rates of high-grade CRS and ICANS (both 8.7%). The ORR was high at 95.5% (n=21), with 90.9% (n=20) achieving complete response (CR). Twenty patients were in ongoing remission at data cut-off with a median follow-up of 8.8 months. These preliminary findings support further exploration of obe-cel in pediatric R/R B-ALL and planning for the Phase II expansion is underway.

Abstract 4060 – Poster presentation
Title: Chimeric antigen receptor (CAR) T-cell persistence at Month 3 predicts clinical outcomes in adult patients with relapsed/refractory B-cell acute lymphoblastic leukemia (R/R B-ALL) treated with obecabtagene autoleucel (obe-cel)
Session Name: Acute Lymphoblastic Leukemias: Therapies Excluding Allogeneic Transplantation: Poster III
Session Date and Time: December 8, 2025; 6:00 – 8:00pm ET
Session Room: Orange County Convention Center; West Halls B3-B4
Publication Number: 5118
Presenting Author: Claire Roddie, MD, PhD, FRCPath, Associate Professor Haematology and Honorary Consultant Haematologist, Cancer Institute, University College London (UCL)

Summary: Of 99 patients who achieved remission (CR/CRi) in the FELIX study, 79 (79.8%) had ongoing remission at month three following obe-cel infusion and comprised the subgroup of interest for the analyses. At month three post infusion, 60/79 patients (75.9%) had ongoing CAR T-cell persistence, while 19/79 patients (24.1%) had loss of persistence. In patients who remained in remission beyond month three, including those with deep MRD-negative remission and no post obe-cel SCT, ongoing CAR T-cell persistence at month three, measured by droplet digital PCR (ddPCR), was associated with longer event-free survival (EFS) and overall survival (OS) compared with loss of persistence. These results suggest that persistence status at month three may be a marker for predicting long-term outcomes following obe-cel treatment in patients with r/r B-ALL.

Abstract 4031 – Poster presentation
Title: Evaluation of commercially available chimeric antigen receptor (CAR) detection reagents for monitoring of CAR T-cell (CAR T) expansion and persistence in patients (pts) treated with obecabtagene autoleucel (obe-cel)
Session Name: Cellular Immunotherapies: Early Phase Clinical Trials and Toxicities: Poster I
Session Date and Time: December 6, 2025; 5:30 – 7:30pm ET
Session Room: Orange County Convention Center; West Halls B3-B4
Publication Number: 2367
Presenting Author: Rehan Hussain, Translational Medicine Senior Scientist

Summary: Measuring obe-cel expansion and persistence using flow cytometry (FC) is feasible with commercially available antibodies that directly target regions of the CAR construct, such as the G4S linker. These reagents show high correlation with anti-idiotype antibodies and provide a reliable method for tracking CAR expression in patients. Use of the G4S binder enabled tracking of CAR T expansion kinetics and phenotypic profiles in patients with different disease burdens. Reagents based on the CD19 protein, commonly used in other CAR T therapies, are unsuitable for obe-cel due to the unique features of the CAT19 binder, which limits effective detection.

Abstract 4429 – Oral presentation
Title: Impact of chimeric antigen receptor (CAR) product cell phenotypes on clinical outcomes following treatment with obecabtagene autoleucel (obe-cel)
Session Name: Acute Lymphoblastic Leukemias: Biomarkers, Molecular Markers, and Measurable Residual Disease in Diagnosis and Prognosis: Prognostic Genetic and Therapeutic Response Factors in Adult and Pediatric B-ALL
Session Date and Time: December 6, 2025; 10:00 – 10:15am ET
Session Room: Orange County Convention Center; W224CDGH
Publication Number: 33
Presenting Author: Benjamin Simpson, Ph.D., Bioinformatics & Data Management Principal Scientist, Autolus Therapeutics

Summary: Clinical data show the potential for obe-cel to produce long-term outcomes. This analysis details certain product features potentially affecting clinical outcomes, including how drug product phenotypes correlate with treatment outcomes following infusion with obe-cel. A higher percentage of central memory cells (Tcm) in the drug product samples was an independent predictor of positive clinical outcomes, including overall survival (OS), following obe-cel infusion. While the T-cell phenotype composition in the leukapheresis product (LP) was weakly correlated with that in the drug product, CD25+ HLADR+ CD4+ cells in the LP independently predicted less favorable clinical outcomes. However, other factors (e.g. tumor characteristics) are also likely to affect outcomes; therefore, further investigations are needed to better understand and predict favorable clinical outcomes, and to potentially guide studies of additional cell manipulations during CAR T-cell manufacturing.

(Press release, Autolus, DEC 8, 2025, View Source [SID1234661277])