Development of a PD-L1 PET Imaging Biomarker
Grade Level at Time of Presentation
Senior
Major
Biology
Minor
Philosophy& Chinese Language
Institution
University of Louisville
KY House District #
42
KY Senate District #
35
Faculty Advisor/ Mentor
Haixun Guo, PhD.
Department
Dept. of Biology
Abstract
Immunotherapy strategies are very promising treatments for cancer patients. Specifically, Immune checkpoint inhibitor therapy focusing on the PD-1/PD-L1 pathway shows long-lasting positive results in many cancer patients. Unfortunately, not all the patients can benefit from this highly effective treatment. Hence, there is a great need for predictive biomarkers. Immunohistochemical (IHC) staining has been used as a way of predicting patient response, yet shows many problems. For example, IHC utilizes an invasive biopsy and sample fixing, which creates an incomplete and delayed picture of the patient’s biochemistry and the tumor microenvironment, consequently ignoring metastases.
The purpose of this study is to develop PET imaging biomarkers for predicting immunotherapy outcomes.
To synthesize the PD-L1 PET imaging biomarker, a F(ab’)2 antibody fragment was created by pepsin digestion of IgG anti-mouse PD-L1 antibody. This product was purified via SEC FPLC and characterized by SDS-Page. Then the chelator Deferoxamine-SCN (Df) was covalently conjugated onto the F(ab’)2 fragment. To create a viable imaging agent, the Df-F(ab’)2 protein was radiolabeled with Zirconium-89. This radiolabeled 89Zr-Df-F(ab’)2 protein was then injected into naïve and B16F10 melanoma mice for imaging and biodistribution to determine the imaging contrast and pharmacokinetics of the developed biomarker.
The radiolabeled antibody fragment PET imaging biomarker, 89Zr-Df-F(ab’)2, was successfully synthesized with high radiochemical yield and PD-L1-specificity. 89Zr-Df-F(ab’)2 showed superior imaging contrast in B16F10 melanoma-bearing C57 black mouse models at 2 hours post-injection when compared to the full antibody counterpart. Biodistribution data showed a significant reduction in liver uptake of the fragmented imaging agent as well.
The PD-L1 PET imaging biomarker 89Zr-Df-F(ab’)2 was successfully synthesized, purified, and characterized. In the B16F10 melanoma C57 black mouse model the developed 89Zr-Df-F(ab’)2 shows superior imaging contrast over its full antibody counterpart. This novel biomarker offers the ability to monitor PD-L1 levels in live animal models, and potentially cancer patients for a more personalized immune checkpoint inhibitor treatment.
Development of a PD-L1 PET Imaging Biomarker
Immunotherapy strategies are very promising treatments for cancer patients. Specifically, Immune checkpoint inhibitor therapy focusing on the PD-1/PD-L1 pathway shows long-lasting positive results in many cancer patients. Unfortunately, not all the patients can benefit from this highly effective treatment. Hence, there is a great need for predictive biomarkers. Immunohistochemical (IHC) staining has been used as a way of predicting patient response, yet shows many problems. For example, IHC utilizes an invasive biopsy and sample fixing, which creates an incomplete and delayed picture of the patient’s biochemistry and the tumor microenvironment, consequently ignoring metastases.
The purpose of this study is to develop PET imaging biomarkers for predicting immunotherapy outcomes.
To synthesize the PD-L1 PET imaging biomarker, a F(ab’)2 antibody fragment was created by pepsin digestion of IgG anti-mouse PD-L1 antibody. This product was purified via SEC FPLC and characterized by SDS-Page. Then the chelator Deferoxamine-SCN (Df) was covalently conjugated onto the F(ab’)2 fragment. To create a viable imaging agent, the Df-F(ab’)2 protein was radiolabeled with Zirconium-89. This radiolabeled 89Zr-Df-F(ab’)2 protein was then injected into naïve and B16F10 melanoma mice for imaging and biodistribution to determine the imaging contrast and pharmacokinetics of the developed biomarker.
The radiolabeled antibody fragment PET imaging biomarker, 89Zr-Df-F(ab’)2, was successfully synthesized with high radiochemical yield and PD-L1-specificity. 89Zr-Df-F(ab’)2 showed superior imaging contrast in B16F10 melanoma-bearing C57 black mouse models at 2 hours post-injection when compared to the full antibody counterpart. Biodistribution data showed a significant reduction in liver uptake of the fragmented imaging agent as well.
The PD-L1 PET imaging biomarker 89Zr-Df-F(ab’)2 was successfully synthesized, purified, and characterized. In the B16F10 melanoma C57 black mouse model the developed 89Zr-Df-F(ab’)2 shows superior imaging contrast over its full antibody counterpart. This novel biomarker offers the ability to monitor PD-L1 levels in live animal models, and potentially cancer patients for a more personalized immune checkpoint inhibitor treatment.