# Structure, Function and Mechanistic Analysis of LAG3

> **NIH NIH R01** · UNIVERSITY OF PITTSBURGH AT PITTSBURGH · 2024 · $783,023

## Abstract

PROJECT SUMMARY
LAG3 (CD233) is an inhibitory receptor that plays a critical role in controlling T cell tolerance, preventing
autoimmunity and limiting immune-mediated tissue damage. It is highly upregulated on exhausted T cells in
tumors and in chronic viral infections, limiting the development of sterilizing immunity. Consequently, LAG3 is
now a major immunotherapeutic target for the treatment of cancer and other diseases. In early 2022, the FDA
approved a combinatorial treatment with anti-PD1 and anti-LAG3 for treatment of metastatic melanoma. Despite
extensive analysis of LAG3 for over 33 years and with more than 20 LAG3 targeting therapeutic antagonists in
the clinic, there is still a considerable number of critical, unanswered questions regarding how LAG3 works and
thus whether we have, and how we might develop, not only more optimal LAG3-targeting therapeutic antagonists
but also therapeutic agonists to treat autoimmune and inflammatory diseases. Therefore, our goal for this
proposal is to gain critical insight into the requirements for optimal LAG3 function enabling us to design more
efficacious immunotherapeutic strategies that block or enhance LAG3 function.
AIM 1: Determine the impact of EP-mediated LAG3 signaling and its importance relative to other motifs.
We will address 2 questions: (A) What is the importance of the LAG3 EP motif in vivo relative to other motifs?
(B) What is the relative importance, hierarchy and functional impact of all LAG3 motifs?
AIM 2: Define LAG3-TCR/CD3 association and its functional relevance compared to MHCII and FGL1. We
will address the structural basis for the biological function of LAG3 by asking 4 questions: (A) Which
regions/residues mediate LAG3 interaction with TCR/CD3 and are they distinct from those that mediate MHCII
or FGL1 interaction? (B) What is the relative importance of LAG3 association with TCR/CD3 versus MHCII and
FGL1 in mediating its function? (C) Do current clinical antibodies disrupt LAG3 association with TCR/CD3 and/or
FGL1 relative to MHCII? (D) Can we enhance LAG3 function?
AIM 3: Define the functional impact of LAG3 dimerization. We will address 3 questions: (A) What are the
functional consequences of monomeric versus dimeric LAG3? (B) Does the proportion LAG3 dimer on the cell
surface change depending upon activation status? (C) Can LAG3 dimerization be modulated by anti-LAG3
mAbs?
Given our extensive analysis of LAG3 function for ~25 years, the unique tools we have in hand, and our
strong and technically diverse collaborative team, we are ideally positioned to conduct this research.
Successful completion of this project will significantly enhance our understanding of LAG3 function and
mechanism of action, providing key insight to generate enhanced LAG3 therapeutics that can improve
treatment for multiple diseases.

## Key facts

- **NIH application ID:** 10874824
- **Project number:** 2R01AI144422-06
- **Recipient organization:** UNIVERSITY OF PITTSBURGH AT PITTSBURGH
- **Principal Investigator:** Roy A Mariuzza
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $783,023
- **Award type:** 2
- **Project period:** 2019-01-08 → 2028-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10874824

## Citation

> US National Institutes of Health, RePORTER application 10874824, Structure, Function and Mechanistic Analysis of LAG3 (2R01AI144422-06). Retrieved via AI Analytics 2026-06-01 from https://api.ai-analytics.org/grant/nih/10874824. Licensed CC0.

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