Chimeric Antigen Receptor T Cells Directed Against CD19 Induce Durable Responses and Transient Cytokine Release Syndrome in Relapsed, Refractory CLL and ALL

Chimeric antigen receptors (CARs) combine the antigen recognition domain of an antibody with intracellular signaling domains into a single chimeric protein. CD19 is an ideal target for CARs since expression is restricted to normal and malignant B cells. Inclusion of the CD137 (4-1BB) signaling domain results in potent antitumor activity and in vivo persistence of anti-CD19 CARs in mice. We reported anti-tumor activity of CAR-modified autologous T cells targeted to CD19 (CART19 cells) in 3 patients (pts) with CLL with relatively short follow up (Porter, et al NEJM 2011; Kalos et al Sci Trans Med 2011). We now report on outcomes and longer follow up from 10 pts treated with CART19 cells.

Autologous T cells collected by leukapheresis were transduced with a lentivirus encoding anti-CD19 scFv linked to 4-1BB and CD3-z signaling domains. Gene-modified T cells were expanded and activated ex-vivo by exposure to anti-CD3/CD28 beads. Pts had CLL or ALL with persistent disease after at least 2 previous treatments.

10 pts have received CART19 cells; 9 adults median age 65 yrs (range 51–78) were treated for relapsed, refractory CLL and one 7 yr old was treated for relapsed refractory ALL. CLL pts had received a median of 5 prior regimens (range 2–10) and all had active disease at the time of infusion. 3/9 CLL patients had deletion of the p53 gene. The ALL pt had chemorefractory relapse, having received chemotherapy 6 weeks prior to infusion. All CLL pts received lymphodepleting chemotherapy 4–6 days before infusions (FC, PC or bendamustine, while the ALL pt had an ALC <10 after prior chemotherapy and did not require further lymphodepletion). A median of 7.5 × 10⁸ total cells (range 1.7–50) corresponding to 1.45 × 10⁸ (range 0.14–5.9) genetically modified cells were infused on day 0. Median follow-up as of 8/12/2012 was 5.6 mo (range 1–24 mo). 9 pts are evaluable for response (<30d follow up in 1 pt). No pt has died. There were no infusional toxicities >grade 2. CART19 homed to the marrow in the CLL pts and marrow and CSF for the ALL patient with detectable CART19 cells in the CSF (21 lymphs/uL, 78% CAR+) day 23 after infusion. 4/9 evaluable pts achieved CR. (3 CLL, 1 ALL). 2 CLL pts had a PR lasting 3 and 5 months, and 3 pts did not respond. In the 4 pts who achieved CR, maximal expanded cells in the blood were detected at an average of 27 fold higher than the infused dose (range 21–40-fold) with maximal in-vivo expansion between day 10 and 31 post infusion. No patient with CR has relapsed. All pts who responded developed a cytokine release syndrome (CRS) manifested by fever, and variable degrees of nausea, anorexia, and transient hypotension and hypoxia. In responding CLL pts the maximal fold elevation from baseline for IFN-γ was 89–298x, IL-6 6–40x, and IL2R 5– 25x, while no significant elevation in systemic levels of TNFα or IL2 were observed. For the ALL pt, maximal elevations from baseline were: IFNγ: 6040x; IL-6: 988x; IL2R: 56x, while significant elevations in TNFα (17x) and IL2 (163x) were also observed. The timing for maximum cytokine elevation differed but in all cases correlated with peak T cell expansion in the PBMC. 5 pts with CRS required treatment; patient 03 was treated with high dose steroids with resolution of symptoms but only achieved a PR. While steroid treatment had a variable effect on the CRS, we noted that these symptoms were temporally associated with significant elevations in serum IL-6. Accordingly, 4 of these pts were treated with the IL6-receptor antagonist tocilizumab on day 3–10 with prompt resolution of fevers, hypotension and hypoxia. 3 of these patients are evaluable for response and 2 achieved a CR. For the pts in CR, CART19 expression in the blood was documented by flow cytometry at the most recent follow up for each patient: 24 mo (pt 01), 22 mo (pt 02), 3 mo (pt 100), and 2 mo (pt 09).

Autologous T cells genetically engineered to express an anti-CD19 scFv coupled to 4-1BB/CD3-z signaling domains can undergo robust in-vivo expansion, persist for at least up to 2 yrs, and can be associated with a significant CRS that responds to anti-cytokine therapy. CART19 cells can induce potent and sustained responses (6/9 responses, 4 CR) for patients with advanced, refractory and high risk CLL and relapsed refractory ALL.

Porter:Novatis: Patents & Royalties; Celgene: Honoraria; Genentech: Employment; Pfizer: Research Funding. Off Label Use: The use of CART19 cells to treat CD19+ malignancy and the use of tocilizumab to treat cytokine activation syndrome related to CART19 cells. Kalos:University of Pennsylvania: Employment, Patents & Royalties. Levine:TxCell: Consultancy, Membership on an entity's Board of Directors or advisory committees; University of Pennsylvania: financial interest due to intellectual property and patents in the field of cell and gene therapy. Conflict of interest is managed in accordance with University of Pennsylvania policy and oversight Patents & Royalties. June:Novartis: Research Funding, entitled to receive royalties from patents licensed to Novartis, entitled to receive royalties from patents licensed to Novartis Patents & Royalties.