# Novel DNA damage response therapeutics targeting replication protein A

> **NIH NIH R01** · INDIANA UNIVERSITY INDIANAPOLIS · 2022 · $496,895

## Abstract

Novel DNA damage response therapeutics targeting replication protein A
Abstract
The DNA damage response (DDR) is now considered a tractable pathway to target for cancer therapy. The
DDR and DNA repair pathways are also amenable to personalized therapies by exploiting synthetic lethal
interactions as evidenced by the clinical success of PARP inhibitors in homologous recombination (HR)
deficient cancers. The DDR is initiated by engagement of the PI3 kinase-related kinases ATM, ATR, and DNA-
PK. These kinases and the downstream checkpoint kinases CHK1 and CHK2, are clinically validated targets
being actively investigated in multiple clinical trials. A novel target in the DDR pathway is the human single
stranded DNA binding protein, replication protein A (RPA) which plays a critical role in the DDR to detect
replication stress (RS) and signal to the ATR kinase. RS is a common feature in cancer cells and provides the
therapeutic window for the anticancer activity of DDR targeted drugs. RS coupled with a DDR blockade results
in replication catastrophe (RC) and eventually cell death. RPA is a critical protector from RC and depletion of
RPA or “RPA exhaustion” can elicit RC and cell death when there is insufficient single-strand DNA binding
capacity to protect the genomic DNA. We have identified a potent and selective small molecule RPA inhibitor
(RPAi), NERx 329, which possesses biochemical RPA inhibition and cellular engagement of RPA. NERx 329
also displays no overt toxicity in vivo and possesses anticancer activity alone and in combination with DNA
damaging chemotherapeutics and certain DDR targeted agents. While the anticancer activity could be the
result of inhibiting RPA’s role in individual repair or replication pathways, our published and preliminary data
point to a more global mechanism of action. Our overarching hypothesis is that chemical inhibition of
RPA can mimic RPA exhaustion to inhibit the DDR and provide selective anticancer activity via novel
genetic interactions common in lung and ovarian cancer. To address this hypothesis, we will elucidate the
mechanisms and determinants of the cellular anticancer activity of our novel RPAi. We will focus on two
cancers types, high grade serous epithelial ovarian cancer (EOC) and non-small cell lung cancer (NSCLC), as
our analysis of clinical survival data reveals an important role for RPA in these cancers. In Aim 1 we will
interrogate how chemical exhaustion of RPA impacts RS and the DDR in lung and ovarian cancer. Aim 2 will
focus on elucidating the genetic determinants of sensitivity to RPAi’s. We will identify novel chemical-genetic
interactions in a DDR focused CRISPR screen assessing RPAi activity. Clinically relevant genetic interactions
will be identified in a unique series of PD-EOC spheroid lines we have developed. Whole genome sequencing
will identify genetic alterations and chromosomal rearrangements which may correlate with response to RPAi
therapy. From these studies, specific genetic...

## Key facts

- **NIH application ID:** 10432115
- **Project number:** 5R01CA257430-02
- **Recipient organization:** INDIANA UNIVERSITY INDIANAPOLIS
- **Principal Investigator:** JOHN J. TURCHI
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $496,895
- **Award type:** 5
- **Project period:** 2021-07-01 → 2026-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10432115

## Citation

> US National Institutes of Health, RePORTER application 10432115, Novel DNA damage response therapeutics targeting replication protein A (5R01CA257430-02). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10432115. Licensed CC0.

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