Developing Multimodal Multiplexed ImmunoPET-Raman Probes to Guide Immunotherapies

Project Summary/Abstract:
Inhibitors of the PD-1/PD-L1 axis has been successful across multiple diseases. However, only a small subset
of patients respond to these regimen and identifying patients likely to benefit from these therapies remains
challenging. Current clinical standard relies on histopathology that fail to accurately predict PD-L1 due to
spatial and temporal heterogeneities among patients. Further, screening patients for PD-L1 alone is not
predictive of treatment response due to significant variabilities in PD-L1 assays across labs necessitating
simultaneous detection of multiple immunomarkers. This establishes our scientific premise that an urgent
need exists for accurate noninvasive diagnostic tools that enables detection of both PD-L1 and other markers
involved in immune modulation directly in vivo. Whereas ImmunoPET (positron emission tomography) imaging
has transformed our ability to detect single immunomarkers in vivo, multiplexing cannot be achieved with PET
as signal between radionuclides cannot be distinguished. Without the ability to multiplex, patients would
undergo multiple radiotracer dosing and repeated radiation exposure. Further, dynamic changes in
immunomarkers during treatment would be missed as sequential dosing of different radiotracers would require
>1 week wait time between doses to allow for decay of the radiotracers. Our objective is to address the
limitations of current approaches and enable multiplexed detection of both PD-L1 and CD8+ T cells in vivo with
an innovative nanoprobe, immunoactive gold nanoparticles (IGNs). IGNs labeled with antibodies, Raman
reporters, and 89Zr radiotracers synergistically integrates the merits of immunoPET with surface-enhanced
Raman spectroscopy (SERS). SERS, an optical technique, uses near-infrared light to enhance the vibrational
signal of Raman reporters enabling narrow spectral features amenable for multiplexing. Our approach is
unique because clinically-translatable IGNs seamlessly combine the depth-resolved whole body imaging of
PET with the high resolution and multiplexing ability of SERS enabling simultaneous detection of both
immunomarkers in vivo with high specificity. Detection of both immunomarkers in vivo is important because
dynamic changes occur in both PD-L1 and CD8 during and after treatment that are not captured by static
measure of receptors or by single biomarker imaging. Whereas immunomarker detection with IGNs is relevant
to many diseases, we will use mouse models of breast cancer (BC) since PD-L1 and CD8 immunomarkers
play a critical role in BC treatment response. IGNs will detect both PD-L1 and CD8 in orthotopic BC mouse
models (Aim 1), monitor response to immunotherapies (Aim 2), and validate in clinically-relevant humanized
mice (Aim 3). IGNs is a generalizable platform and ultimately our strategy can be mapped onto other diseases
including infection and autoimmunity where PD-L1 and CD8 biomarkers also play a key role. Further, IGNs
can also be targeted to a number of other biomarkers via antibodies facilitating treatment response in multiple
disorders with unprecedented accuracy not achievable with current clinicopathological approaches.

Grant Number: 5R01EB029756-04
NIH Institute/Center: NIH
Principal Investigator: Rizia Bardhan