Persistence of Non Gene-Modified Adoptively Transferred Marrow Infiltrating Lymphocytes (MILs) More Than Five Years Post Transfer

Hallmarks of effective adoptive T cell therapy include: 1) the ability to access and expand T cells of interest 2) measurable anti-tumor efficacy of these cells upon reinfusion and 3) T cell persistence over time. In examining the long-term follow-up of patients treated with MILs, we show evidence of persistence of adoptively transferred MILs for over five years post transfer.

In a clinical trial conducted in 2007, Prevnar naïve myeloma patients were immunized against the modified diphtheria toxin, CRM197 with the Prevnar vaccine administered 2 weeks prior to collecting marrow infiltrating lymphocytes (MILs) from bone marrow. Patients received a CD34-selected (T cell depleted) autologous stem cell transplant (SCT) and had activated and expanded MILs infused 3 days later. As such, 99% of infused T cells were Prevnar-primed, ex vivo expanded MILs. This approach enabled us to track the fate of the non gene-modified MILs by examining CRM197 specific T cells. As originally reported, persistence at one year of both CRM197 and myeloma antigen-specific T cells correlated with clinical responses.¹

Long-term follow up was performed in a subset of the patients that had undergone bone marrow biopsies for clinical purposes. The results showed that patients who had been in a complete response at the end of the clinical trial maintained a greater number of both CRM197 and myeloma antigen-specific T cells over time for up to 7 years after the clinical trial. Patients who did not achieve a complete response and subsequently relapsed showed a loss of both CRM197 as well as myeloma antigen- specific T cells in most cases. Considering that the patients received a T cell depleted stem cell graft, the CRM197-specific T cells that were measured were likely a result of the Prevnar-primed MILs.

From these results, we conclude that: 1) adoptively transferred CRM-197 specific MILs showed persistence up 7 years following their infusion. 2) the magnitude of CRM197 and myeloma antigen-specific T cell responses correlated with clinical responsiveness. Taken together, these data demonstrate several unique attributes of MILs which are critical for successful adoptive T cell therapy

1. Adoptive transfer of activated marrow-infiltrating lymphocytes induces measurable antitumor immunity in the bone marrow in multiple myeloma. Noonan KA, Huff CA, Davis J, Lemas MV, Fiorino S, Bitzan J, Ferguson A, Emerling A, Luznik L, Matsui W, Powell J, Fuchs E, Rosner GL, Epstein C, Rudraraju L, Ambinder RF, Jones RJ, Pardoll D, Borrello I. Sci Transl Med. 2015 May 20;7(288).