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4650 Dual Antigen Targeting with Co-Transduced CD19/22 CAR T Cells May Prevent Antigen-Negative Relapse after CAR T Cell Therapy for Relapsed/Refractory ALL

Program: Oral and Poster Abstracts
Session: 704. Cellular Immunotherapies: Early Phase and Investigational Therapies: Poster III
Hematology Disease Topics & Pathways:
Research, clinical trials, Lymphoid Leukemias, ALL, Biological therapies, Clinical Research, Chimeric Antigen Receptor (CAR)-T Cell Therapies, Diseases, Therapies, Lymphoid Malignancies
Monday, December 12, 2022, 6:00 PM-8:00 PM

Sara Ghorashian, FRCPath, PhD1,2, Giovanna Lucchini, MD3*, Rachel Richardson, MSc4*, Kyvi Nguyen, MSc5*, Craig Terris, BSc5*, Macarena Oporto-Espuelas, MD5*, Jenny Yeung, PhD6*, Danielle Pinner3*, Jan Chu3*, Lindsey Williams7*, Ka-yuk Ko7*, Chloe Walding8*, Kelly Watts9*, Sarah Inglott10*, Stuart Adams, PhD11*, Emma Gravett10*, Kimberly Gilmour, PhD12*, Alka Lal13*, Sangeetha Kunaseelan13*, Bilyana Popova, MSc14*, Andre Lopes15*, Yenting Ngai, PhD16*, Evangelia K Kokalaki, PhD17*, Milena Balasch Carulla, MD7*, Khushnuma Mullanfiroze, MD7*, Arina Lazareva, MD3*, Vesna Pavasovic, MD10*, Anupama Rao, MD10*, Jack Bartram, MD, PhD10*, Ajay Vora, MD18, Robert Chiesa, MD19*, Juliana Silva, MD7*, Kanchan Rao, MD3*, Katherine Clesham, MD PhD20*, Denise Bonney, MD21*, Robert F Wynn, MD22, Martin Pule, MD, PhD23*, Rachael E Hough, MD24* and Persis J Amrolia, MD PhD7,25*

1Department of Hematology, Great Ormond Street Hospital for Children, London, United Kingdom
2Developmental Biology and Cancer, UCL Great Ormond Street Institute of Child Health, London, ENG, United Kingdom
3Department of Blood and Marrow Transplantation, Great Ormond Street Hospital for Children, London, United Kingdom
4Molecular and Cellular Immunology Section, UCL Great Ormond Street Institute of Child Health, London, United Kingdom
5UCL Great Ormond Street Institute of Child Health, Molecular and Cellular Immunology, London, United Kingdom
6UCL Great Ormond Street Institute of Child Health, London, ENG, United Kingdom
7Bone Marrow Transplantation, Great Ormond Street Hospital for Children, London, United Kingdom
8Cancer Clinical Trials Unit, University College London Hospitals NHS Trust, London, United Kingdom
9Bone Marrow Transplantation, Royal Manchester Children's Hospital, Manchester, United Kingdom
10Department of Haematology, Great Ormond Street Hospital for Children, London, United Kingdom
11SIHMDS-Haematology, Great Ormond Street Hospital for Children, London, United Kingdom
12Department of Immunology, Great Ormond Street Hospital for Children, London, United Kingdom
13CRUK Cancer Trials Centre, University College London, London, United Kingdom
14CRUK UCL Cancer Trials Centre, UCL, London, United Kingdom
15Cancer Research UK and UCL Cancer Trials Centre University College London, London, United Kingdom
16UCL CRUK Cancer Trials Centre, University College London, London, United Kingdom
17Autolus Ltd, London, United Kingdom
18Department of Haematology, The Children's Hospital, London, United Kingdom
19Bone Marrow Transplantation, Great Ormond Street Hospital for Children, London, ENG, United Kingdom
20Department of Haematology, University College London Hospitals NHS Trust, London, United Kingdom
21Department of Bone Marrow Transplantation, Royal Manchester, Manchester, United Kingdom
22Royal Manchester Children's Hospital, Manchester University NHS Foundation Trust, Manchester, United Kingdom
23Cancer Institute, University College London, London, United Kingdom
24Haematology, UCLH, London, United Kingdom
25UCL Great Ormond Street Institute of Child Health, London, United Kingdom

Background: CD19 negative escape is a major cause of relapse after CD19 CAR T cell therapy for relapsed/refractory (r/r) paediatric Acute Lymphoblastic Leukemia (ALL) and dual targeting of CD19/CD22 may overcome this. We have previously shown that AUTO1, a fast off rate autologous CD19 CAR T cell therapy was highly active in ALL with a favorable safety profile and excellent persistence (Ghorashian et al Nat.Med. 2019). Building on these properties, we developed AUTO1/22 an autologous CAR T cell product co-transduced with two different lentiviral vectors encoding our existing CD19 CAR and a novel CD22CAR designed to recognise targets with low antigen density. We have evaluated the safety and biological efficacy of AUTO1/22 in a Phase I study in children/young adults with r/r ALL (NCT02443831).

Methods: Patients with r/r B-ALL age < 25 yrs who were ineligible for/relapsed after Tisagenlecleucel were recruited. Following fludarabine/cyclophosphamide lymphodepletion, patients received 1x106 /kg CAR+ T cells. The presence of CAR T cells in the blood/bone marrow (BM) was assessed by flow cytometry + qPCR and BM MRD was assessed by IgH qPCR + flow cytometry. Primary endpoints were incidence of grade 3-5 toxicity and the proportion of patients achieving MRD negative remission.

Results: 12 patients have been treated. The median age was 12 years (range 3-21) and patients had a median of 3 prior lines of therapy (range 2-6). Six of 12 patients had relapsed post allogeneic SCT, 6 had received prior Blinatumomab/Inotuzumab and 4 had relapsed after prior Tisagenlecleucel. Prior to lymphodepletion, 4 patients had >5% BM disease by morphology/flow, 5 had detectable BM MRD and 3 were BM MRD negative. Six patients had extramedullary relapse (of which 2 had non-CNS EM disease). Three had detectable CD19 negative disease at enrolment. One of these was completely CD19 negative and in addition had a 5% CD22 negative population.

CAR T cell products had a central memory phenotype with predominance of CD19/22CAR double positive cells (median 54.4%) and balanced populations of CD19 and CD22 single positive cells (13.1% and 11.6% respectively).

Cytokine release syndrome (CRS) occurred in 11/12 patients (grade 1 n=5, grade 2 n=6) requiring Tocilizumab in 5 cases, but severe (≥ grade 3) CRS was not seen and no patients required ICU admission for CRS. Grade 1-2 ICANS was observed in 5 patients. One patient had delayed grade 4 leucoencephalopathy (MRI/brain biopsy were more indicative of fludarabine toxicity than CAR T related) and has ongoing neurological recovery. Nine patients had grade 3-4 cytopenia persisting beyond/recurring after day 28, requiring a CD34+ stem cell top up in 1 case.

Flow cytometry showed significant initial expansion of all 3 CAR +ve populations early post-infusion but CD19/22CAR double positive cells were lost at later time points. Six patients had circulating CAR T cells by qPCR at last follow up and the median duration of B cell aplasia has not been reached. Ten of 12 patients (83%) achieved MRD negative CR/CRi at one month post-infusion and 2 patients did not respond. Importantly 2/3 patients with CD19-ve disease achieved molecular CR demonstrating the efficacy of our CD22CAR. Of the 10 responding patients, 2 have relapsed with CD19+CD22+ disease, one patient with CD19-ve disease pre-infusion has relapsed with CD19partialCD22+ disease and one had emergence of MRD level disease, in all cases associated with loss of CAR T cells. One other patient had early loss of CAR T cells with B cell recovery but ongoing MRD negative CR at 3 months post-infusion and remains in MRD negative CR on maintenance chemotherapy. Overall, at a median follow-up of 8.7 months (range 1-15 months), 6/10 responding patients remain in MRD negative CR at last follow-up. Importantly, antigen-negative relapse has not been observed.

Summary/Conclusion: Our data show that dual CD19/22 targeting CAR T cells generated by co-transduction show a favorable safety profile, with robust expansion/persistence and early efficacy in a heavily pre-treated cohort.

To date with we have not observed antigen negative relapse. This contrasts to an incidence of 5/6 CD19 negative relapses in the 12 responders treated with single CD19 targeting CAR T cells (AUTO1) in an earlier cohort and suggests dual targeting may be effective in preventing antigen escape. However, longer follow up will be needed to confirm this.

Disclosures: Ghorashian: UCLB: Patents & Royalties; Novartis: Honoraria, Speakers Bureau. Yeung: Bristows LLP, 100 Victoria Embankment, London EC4Y 0DH: Consultancy; UCL Business: Patents & Royalties: WO2022064191A1 Named inventor; ADC Therapeutics: Patents & Royalties: WO2022063853A1 Named inventor; Quell Therapeutics: Consultancy. Kokalaki: Autolus Ltd: Current Employment. Pule: Autolus Ltd: Current Employment, Current equity holder in publicly-traded company. Amrolia: Bluebird Bio: Research Funding; Pierre Fabre: Consultancy; UCL Business: Patents & Royalties; Bluebird Bio: Research Funding; Pierre Fabre: Consultancy; Autolus: Patents & Royalties, Research Funding; ADC Therapeutics: Patents & Royalties: named inventor WO2022063853A1.

OffLabel Disclosure: AUTO1/22 CAR T cells are being investigated and are not currently licensed for therapy of disease

*signifies non-member of ASH