# MELANOMA LOCALIZING RADIOPHARMACEUTICALS

> **NIH NIH R01** · ASSOCIATED UNIV-BROOKHAVEN NATL LAB · 1988 · $179,119

## Abstract

Melanin seeking compounds as melanoma localizing or therapeutic agents have
a major limitation in that the normal melanin containing structures are
frequently encountered clinically as background in the location of the
tumor.  This limits the usefulness of these compounds for therapy and
diagnosis as they are bound to pre-formed melanin in both tumor and normal
tissue.  Our clinical experience with an iodine-123 (I-123) labeled
quinoline derivative was unsuccessful in localizing choroidal melanoma.
This was in part due to the high background uptake of the melanin
containing structures of the eye as well as the high uptake by the brain.
However, the need in clinical ophthalmology for the melanoma localizing
agent is now greater because of the increased use of radiotherapy wherein
no tissue diagnosis is obtained.  The difficulties in differentiating
choroidal nevi from small malignant melanoma continues to plague
ophthalmology.

Small animal data show that the false melanin precursor thiouracil (TU) has
a high concentration in Harding-Passey melanoma (approximately 10% dose/g),
while retention in other tissues is approximately 100 times less.  The
uptake by other pigmented tissues such as the choroid of the eye is low, as
incorporation of TU occurs only as melanin is being formed.  The purpose of
this study is to investigate the therapeutic and diagnostic potential of
labeled thiouracil in humans.  We have successfully synthesized I-125-TU,
and found that it was incorporated into the biosynthetic pathway of melanin
to the same degree as TU itself.  Uptake studies of I-125-TU in our murine
melanoma were so encouraging that extension to clinical trials now seems
appropriate.  It is anticipated that I-123-TU will be useful in the
diagnosis of human melanoma.  Therapy studies with sulfur-35-TU (S-35) in
our Harding-Passey model demonstrated that tumor growth could be suppressed
for 2 to 3 weeks.  Further animal studies are planned before clinical
trials in humans.  However our preliminary data indicates that S-35-TU, or
perhaps more likely I-131-TU, will find a useful place in the radiotherapy
of human melanoma.

## Key facts

- **NIH application ID:** 3171497
- **Project number:** 5R01CA033725-06
- **Recipient organization:** ASSOCIATED UNIV-BROOKHAVEN NATL LAB
- **Principal Investigator:** SAMUEL PACKER
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 1988
- **Award amount:** $179,119
- **Award type:** 5
- **Project period:** 1983-02-01 → 1989-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/3171497

## Citation

> US National Institutes of Health, RePORTER application 3171497, MELANOMA LOCALIZING RADIOPHARMACEUTICALS (5R01CA033725-06). Retrieved via MORVS 2026-10-25 from https://api.morvs.ai/grant/nih/3171497. Licensed CC0.

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