Prolonged T Cell Persistence, Homing to Marrow and Selective Targeting of Antigen Positive Tumor in Multiple Myeloma Patients Following Adoptive Transfer of T Cells Genetically Engineered to Express an Affinity-Enhanced T Cell Receptor Against the Cancer Testis Antigens NY-ESO-1 and Lage-1

Adoptive transfer of T cells genetically engineered to express affinity-enhanced T cell receptors (TcRs) specific for self-antigens is one approach to generate potent anti-tumor immunity, and this approach is being evaluated in a number of clinical trials. Although persistence of engineered T cells is positively correlated with response rates, a recurring observation to-date has been poor T cell persistence beyond the initial treatment window. We have recently initiated a Phase II clinical trial (NCT01352286) in patients with recurrent multiple myeloma (MM), to evaluate the safety and activity of autologous T cells genetically engineered to express an HLA-A201 restricted, affinity-enhanced TCR that targets an epitope shared by the NY-ESO-1 and LAGE-1 cancer testis antigens commonly expressed by MM. Clinical study details and outcomes are reported elsewhere in this meeting (Rapoport, A, Stadtmauer, E. et al.). Here we report the in vivo expansion, bioactivity, trafficking, durable persistence, and anti-tumor activity of TcR modified cells in this trial.

Subjects received high-dose melphalan, infusion of autologous hematopoietic stem cells on day 0, and infusion of gene engineered cells (GEC) on day +2. Persistence of GEC was assessed by quantitative ABI-Taqman based PCR and a qualified assay that detects the lentivirus backbone sequence. Surface expression of the introduced affinity-enhanced TcR α/β receptor was detected by multiparametric flow cytometry and TcR-specific dextramer™reagents. NY-ESO-1 and LAGE-1 antigen expression in marrow samples was assessed by quantitative ABI-taqman based PCR and inventoried primer/probe sets.

As of August 2012, we have screened marrow from 46 patients for NY-ESO- and LAGE-1 expression. Of these, 29 (63%) and 17 (37%) expressed LAGE-1 and NY-ESO-1, respectively by PCR. LAGE-1 co-expression was observed in all cases with NY-ESO-1. To date 12 patients have been infused with GEC. Robust engraftment was observed, with peak levels of gene-marked cells in peripheral blood and marrow ranging from 1 × 10²-1 × 10³ cells/μL and peak levels detected within the first 21 days post infusion. By day +100 the absolute number of GEC showed patient-specific and variable contraction, with a subset of patients maintaining GEC at 1 × 10²-1 × 10³ cells/μL, and a second subset where GEC contracted to 1 × 10¹-1 × 10²cells/μL. Trafficking to and persistence of GEC in marrow was observed. At both early (up to day +30) and, in a subset of patients, late timepoints (post day+42), circulating CD3+ T cells could be detected with surface expression of the affinity enhanced TcR. Engineered cells are detected in all patients at their latest timepoint by Q-PCR. To date we see no evidence for TCR mispairing with endogenous TCR.

Tumor-antigen and tumor-specific targeting by GEC was evaluated using Q-PCR and quantifying transcript levels of NY-ESO-1, LAGE-1, and CD138 (as a plasma cell marker) in marrow biopsies at enrollment, and days +42, +100, and +180. In the initial cohort of 5 patients, selective reappearance of CD138 transcript is observed in 4 cases (2 sCR, 1 VGPR, 1 PR), with non-detectable or very weak expression of LAGE-1/NY-ESO-1 transcripts, suggesting specific targeting of tumor cells that express LAGE-1/NY-ESO-1. In the fifth patient, who has progressive disease and low engineered cell persistence, CD138 and LAGE-1/NY-ESO-1 transcripts are both present above pre-treatment levels. A second infusion was recently given to this patient.

Our studies show for the first time that adoptive transfer of affinity-enhanced TCR engineered T cells in MM patients results in prolonged T cell persistence, homing to marrow, and anti-tumor activity.

Binder-Scholl:Adaptimmune: Employment. Smethurst:Adaptimmune Ltd: Employment. Brewer:Adaptimmune Ltd: Employment. Bennett:Adaptimmune Ltd: Employment. Gerry:Adaptimmune Ltd: Employment. Pumphrey:Adaptimmune Ltd: Employment. Tayton-Martin:Adaptimmune Ltd: Employment. 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, 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. Jakobsen:Adaptimmune Ltc: Employment. June:Novartis: Research Funding, entitled to receive royalties from patents licensed to Novartis, entitled to receive royalties from patents licensed to Novartis Patents & Royalties.