Clinical Development of Immunotherapies for Rare Hematologic Maligancies

Division Of Basic Sciences - Nci

Investigators

Linked publications, trials & patents

Abstract

CD33 is a cell surface glycoprotein involved in normal myelopoiesis and is expressed on 80% of AML cells. Higher CD33 surface expression has been associated with inferior clinical outcomes in both children and adults with de novo AML. Several trials have demonstrated the safety and efficacy of targeting CD33 in both adult and pediatric AML. Most notable is the experience with gemtuzumab ozogamicin (GO) which has both single-agent activity and has been incorporated with intensive chemotherapy and is FDA approved for the treatment of AML. A recent phase 3 trial demonstrated improved event-free survival (EFS) in pediatric subjects with newly diagnosed AML when GO was incorporated into upfront therapy. Notable toxicities of GO include hepatotoxicity in the form of sinusoidal obstructive syndrome (SOS)/hepatic veno-occlusive disease (VOD). VOD/SOS after GO treatment is most commonly seen in the setting of hematopoietic cellular transplant (HCT). Although GO was removed from the commercial market by the FDA in 2010 based upon some data demonstrating lack of subject benefit, it was re-approved by the FDA in 2017 following new data demonstrating improved outcomes in subjects with AML. Given the outcomes of targeting CD33 with antibody-based therapeutics, CD33 remains an attractive antigen for immunotherapeutic targeting with CAR-modified T cells. Preclinical studies to date have demonstrated robust anti-leukemia activity of CD33 CAR T-cells in in vitro and in vivo AML model systems . We selected CD33 as an optimal target for a first-in-child AML CAR-T cell immunotherapy trial given its prevalent surface expression on AML blasts and the extensive clinical experience demonstrating safety and efficacy of CD33 targeting with gemtuzumab in children and young adults with AML. In preclinical studies used to inform this trial, six second-generation lentivirally-transduced CD33 CAR T-cells using three distinct CD33 ScFv constructs (gemtuzumab, lintuzumab, m195) each with one of two co-stimulatory domains CD3z and CD28 or 4-1BB was tested (manuscript in development). In vitro testing of CD33CARTs against multiple AML cell lines revealed that CD33/CD28zCAR-T cells consistently induced higher IL-2 and interferon-y production than did T cells transduced with CD33/4-1BB CAR constructs. Assessment of the six CD33 CAR T-cells in luciferase+ MOLM14 xenograft models and primary childhood AML patient derived xenograft (PDX) models further demonstrated potent in vivo anti-leukemia activity. Based upon superior preclinical efficacy in our tested models, the CD33.2/CD28z which incorporates the lintuzumab ScFv in the construct was selected and further optimized as the CD33 CAR T-cells clinical construct for this trial. Based on the pre-clinical efforts, a phase 1 trial was planned. The preclinical manuscript was recently accepted to the Journal of ImmunoTherapy of Cancer (Qin et al, JITC 2021, in press). This phase 1/2 trial aims to determine the safety and feasibility of anti-CD33 CAR expressing T cells (CD33CART) in children and adolescents/young adults (AYAs) with relapsed/refractory AML. The trial will be done in two phases: Phase 1 will determine the maximum tolerated dose of CD33CART cells using a 3+3 trial design. Phase 2 is an expansion phase designed to evaluate the rate of response to CD33CART. The CD33 CAR T-trial started enrollment in January 2020. This represents the first AML targeted approach in children with a highly collaborative clinical and translational efforts built into the infrastructure of the trial. We anticipate that several novel observations will emerge from this study. If the CAR construct is safe, feasible and effective, we will work on establishing an adult CD33 CAR T-trial. Secondary objectives for all subjects include: 1) To determine the feasibility of manufacturing CD33CART from subjects with AML and 2) To determine the feasibility of infusing CD33CART in subjects with AML. For the treatment population that receives CD33CART, secondary objectives include: 1) To determine the incidence and severity of CRS, sinusoidal occlusion syndrome (SOS), or other CD33CART related toxicities; 2) To estimate the overall survival, event-free survival, and treatment-related mortality at Day 28 post-CD33CART; 3) To determine the percentage of subjects treated with CD33CART who achieve morphologic remission (5% blasts in marrow) at Day 28 post-CD33CART cell infusion (for those in Phase I); 4) To determine the percentage of subjects treated with CD33CART who achieve molecular remission (for those with an identified molecular marker) at Day 28 post-CD33CART cell infusion; 5) To determine minimal residual disease (MRD) negativity by flow cytometry (0.1%) at Day 28 post-CD33CART cell infusion; and 6) To determine the percentage of subjects able to proceed to allogeneic hematopoietic stem cell transplantation following treatment with CD33CART. Post-HSCT outcomes, including engraftment and SOS will be closely monitored for. Exploratory objectives will be performed collaboratively and under the guidance of the multicenter local PIs and include: 1) To measure CD33CART remission induction by minimal residual disease assessments using research level NGS testing; 2) To correlate responses and CD33CART expansion with immunophenotypic CD33 surface expression, plasma concentrations of soluble CD33, and CD33 genotyping; 3) To quantify CD33CART expansion and in vivo persistence in blood and bone marrow of treated subjects at Day 28 post-CD33CART cell infusion and post-HCT; 4) To evaluate the AML surfacesome/proteogenomics; 5) To assess potential CD33CART-related neurotoxicity; and 6) To assess subject-reported adverse events prior to infusion and weekly in the month following CD33CART infusion