# Maximizing Antibody Drug Conjugate Efficacy through Multiple Mechanisms of Action

> **NIH NIH R35** · UNIVERSITY OF MICHIGAN AT ANN ARBOR · 2022 · $318,224

## Abstract

Abstract
The recent FDA approval of two more antibody drug conjugates (ADCs) highlights the clinical success and
growth in this class of agents. Despite these approvals, however, the attrition rate for new ADCs remains high,
and in oncology applications, no ADC for solid tumors has yet been able to repeat the success of ado-
trastuzumab emtansine (T-DM1). A substantial effort has been exerted to improve the antibody and target
selection, conjugation site, linker stability, and payload properties (potency, bystander effects, etc.), and these
improvements will benefit the next generation of compounds. However, fundamental questions remain on how
to design a clinically effective agent. Specifically, the relative contribution and interaction between the multiple
mechanisms of action of these drugs (receptor signaling blockade, payload efficacy, and Fc effector functions)
remains unknown. The long-term goal is to understand the fundamental properties of these complex drugs in
sufficient detail to rationally combine the antibody, linker, and payload with a particular target (in a select
patient population) for maximum clinical efficacy in both cancer and non-oncologic applications. The goal for
this proposal is to quantitatively understand the relative contribution of direct payload effects in antigen positive
cells, bystander payload effects in antigen negative cells, and the role of Fc-effector functions in determining
efficacy with antibody drug conjugates. Using a combination of near-infrared fluorescence imaging and flow
cytometry, the absolute number of intact and degraded (triggering payload release) ADCs per cell can be
determined. By pairing these results with pharmacodynamic markers (e.g. DNA damage markers of alkylating
agents), the delivery and efficacy of the ADC (both direct and bystander killing) can be quantified with single
cell resolution in vivo. Co-administration of varying ratios of ADC with unconjugated antibody will be used to
control the tissue distribution to vary direct versus indirect killing. The studies will be conducted in both an
immunocompromised and immunocompetent (syngeneic) mouse model to determine the benefit (or
requirement) for immune system activation. By comparing the single-cell measurements with the gold standard
of preclinical efficacy (tumor growth curves), the relative contribution of each mechanism will be determined.
The outcome of the work will enable the rational design of novel ADCs rather than testing the myriad
combinations in vivo by focusing development on a) selection of targets with more uniform expression and
ADC internalization if direct targeting predominates, b) optimal physicochemical properties and distribution of
bystander payloads if bystander effects plays a major role, or c) activation and recruitment of immune cells
through co-therapy, Fc engineering, and/or dosing regimens if immune cell recruitment is necessary. A
significant number of monoclonal antibodies that failed as monotherapi...

## Key facts

- **NIH application ID:** 10462003
- **Project number:** 5R35GM128819-05
- **Recipient organization:** UNIVERSITY OF MICHIGAN AT ANN ARBOR
- **Principal Investigator:** Greg Thurber
- **Activity code:** R35 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $318,224
- **Award type:** 5
- **Project period:** 2018-08-01 → 2023-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10462003

## Citation

> US National Institutes of Health, RePORTER application 10462003, Maximizing Antibody Drug Conjugate Efficacy through Multiple Mechanisms of Action (5R35GM128819-05). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10462003. Licensed CC0.

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