# Developing high throughput measurement of thiopurine in DNA by mass spectrometry

> **NIH NIH R41** · TYMORA ANALYTICAL OPERATIONS, LLC · 2020 · $299,975

## Abstract

PROJECT SUMMARY
Thiopurines such as mercaptopurine are S-substituted antimetabolites used as functional analogs to
natural nucleobase precursors. They are highly effective against hematologic malignancies
(leukemia and lymphoma) and autoimmune diseases (inflammatory bowel diseases [IBD]), with an
estimated patient population >350,000 in the US. However, the cytotoxicity of thiopurines depends
on their conversion into 6-thioguanine (TG) nucleotides (TGN), which are incorporated into DNA,
causing cell death by post-replicative DNA mismatch repair. They have narrow therapeutic indexes
with dose-limiting hematopoietic toxicity whereas low-responders are undertreated with standard
dosing. Therefore, there is enormous clinical benefit from preemptively identifying patients at risk of
thiopurine toxicity and individualizing therapy to mitigate it. We propose here a high throughput
method based on matrix-assisted laser desorption ionization (MALDI) mass spectrometry (MS) for
quantifying the pharmacological endpoint of thiopurines, TG incorporated in chromosomal DNA
(DNA-TG) of white blood cells, and examine its specificity and accuracy in standard and clinical
samples. To test this strategy, we propose three specific aims: Aim #1. Chemical derivatization,
isolation and detection of 6-thioguanine (6-TG) by MALDI-MS. Aim #2. Examination of linear range,
sensitivity, specificity and reproducibility of the method. Aim #3. Validation of high throughput 6-TG
detection with biological samples. With the aim to individualize thiopurine therapy through reducing
adverse reactions and obtaining optimum therapeutic efficacy for patients on thiopurine treatment,
the high throughput technique facilitates continuous monitoring of thiopurine in DNA before and
during the therapy. This highly translational project will likely have high impact on a large number of
patients who are under chemo-treatment or thiopurine therapy for non-malignant conditions (e.g.,
IBD).

## Key facts

- **NIH application ID:** 9909135
- **Project number:** 1R41GM136093-01
- **Recipient organization:** TYMORA ANALYTICAL OPERATIONS, LLC
- **Principal Investigator:** W. Andy Tao
- **Activity code:** R41 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $299,975
- **Award type:** 1
- **Project period:** 2020-04-02 → 2023-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9909135

## Citation

> US National Institutes of Health, RePORTER application 9909135, Developing high throughput measurement of thiopurine in DNA by mass spectrometry (1R41GM136093-01). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/9909135. Licensed CC0.

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