Pilot Study of T-APCs Following CAR T Cell Immunotherapy for CD19+ Leukemia

This pilot study seeks to examine the feasibility and safety of administering T cell antigen
presenting cells (T-APCs) designed to reactivate and numerically expand CD19-specific CAR T
cells. The underlying hypothesis to be examined is that after remission is achieved with CAR
T cell treatment, the duration, magnitude, and activation state of persisting memory CAR T
cells impact on the potential for durable leukemia eradication. This is of particular
relevance in several groups of patients we have identified: those who are predicted to lose
persistence of their CAR T cells before Day 63, or those who have definitively lost
persistence of CAR T cells prior to 6 months. By providing these patients with episodic
exposure to T-APCs capable of activating CD19-specific CAR T cells for proliferation and
redistribution to tissue beds where tumor cells of ALL seed, ideally over several months
following remission induction, it is posited that the incidence of disease relapse will be
diminished.

Inclusion Criteria:

- Previous treatment under protocol PLAT-02

- Adequate performance status

- Adequate renal, liver, cardiac, and respiratory function

- Adequate absolute lymphocyte count

- HIV negative; Hepatitis B and C negative within 3 months prior to enrollment.

- Patient has sufficient stored T cell product to manufacture appropriate doses of
T-APCs

Exclusion Criteria:

- Evidence of active clinically significant CNS dysfunction

- Evidence of active malignancy other than CD19+ malignancy

- Evidence of active GVHD, or on immunosuppressive GVHD therapy within 4 weeks prior to
enrollment