Immunotherapy – Biomechanisms
Cindy L. Schwartz1, Robyn A. A. Oldham1,2, Mary L. Faber1, A. Thakur3, Lawrence G. Lum3, Jeffrey A. Medin1,2,4
1 Department of Pediatrics, Medical College of Wisconsin, Milwaukee, USA, 2 Department of Medical Biophysics, University of Toronto, Toronto, Canada, 3 Department of Medicine, Division of Hematology/Oncology, University of Virginia Cancer Center, Charlottesville, VA, USA, 4 Department of Biochemistry, Medical College of Wisconsin, Milwaukee, USA
Hodgkin Lymphoma (HL) is highly treatable, but 15–25% of patients have refractory disease or relapse. Chemotherapy resistant disease is challenging to treat: novel therapeutic strategies are needed for this subset of patients. A recent approach to HL immunotherapy is CD30 targeting with brentuximab vedotin, an FDA approved α-CD30 antibody-drug conjugate (ADC).
The efficacy of antibody therapy is based on target, epitope, and affinity. One of our objectives is to develop novel anti-CD30 antibodies with varying binding properties. We will then generate anti-CD30/anti-CD3 bispecific antibodies (bi-mAbs) and CARs for clinical development. Bispecific CD30/CD3 antibodies provide conceptual advantages over naïve antibody therapies by possibly increasing effectiveness and reducing potential side effects associated with conjugated cytotoxic compounds in ADC therapy.
Methods: We generated 15 anti-human CD30 hybridoma cell lines by immunization of mice with purified recombinant huCD30-GST protein that we made. Five hybridomas were selected for further analyses. All candidates showed specific binding to CD30 by flow cytometry and ELISAs, and were characterized by DNA and protein sequencing. Our purified CD30 antibodies were then heteroconjugated with anti-huCD3 antibodies for in vitro/in vivo analyses. Our conjugated antibodies bind both tumor cells and T cells. Subsequent in vitro assessments will test their ability to trigger target cell death. For in vivo studies, CD30 bi-mAbs will be administered to C57BL/6 mice, or pre-incubated with human T cells and administered to NRG mice bearing eGFP/luciferase-expressing huCD30+ lymphoma grafts. In vivo treatment efficacy will be monitored by overall mouse survival and tumor growth/regression, tracked by bioluminescent imaging.
Results: Characterization studies showed that 4 of our antibodies bound to a similar CD30 epitope, while a 5th bound a separate site. Both epitopes are distinct from that bound by brentuximab vedotin. Characterization of antibody affinity and analyses of biological and cytotoxic effects of each antibody is underway.
Conclusions: We developed antibodies that target unique CD30 epitopes and allow us to prepare bispecific CD30/CD3 antibodies. The addition of anti-CD3, will potentially enhance immune response to the tumor. Ultimately, we aim to test our optimized bi-mAb in clinical trials, with the goal of improving survival for HL patients presenting with relapsed/refractory disease.