Prelude Therapeutics (NASDAQ: PRLD) just got the green light from the FDA to move PRT13722, its experimental breast cancer drug, into human testing.

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The FDA cleared Prelude's Investigational New Drug application, allowing the company to begin a Phase 1 trial in patients with advanced or metastatic HR-positive, HER2-negative breast cancer. Enrollment is expected to begin during the fourth quarter.

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If you’re unfamiliar, PRT13722 is an oral drug designed to selectively destroy a protein called KAT6A, which can help cancer cells grow and survive. Rather than simply blocking KAT6A, Prelude's drug is designed to tag the protein for destruction by the body's own cellular machinery.

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There's already clinical evidence suggesting that targeting the broader KAT6 family can work in breast cancer. But existing drugs targeting both KAT6A and KAT6B have also produced side effects that could make them harder to combine with other cancer treatments.

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Prelude thinks it may have a way around that.

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The workaround

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PRT13722 is designed to go after KAT6A while largely leaving KAT6B alone. In preclinical studies, the company says that selectivity produced encouraging antitumor activity while potentially reducing the blood-related toxicities associated with drugs that inhibit both proteins. That's still preclinical evidence, of course. We won't know whether those advantages translate to humans until the clinical data start coming in.

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The upcoming Phase 1 trial will evaluate PRT13722 both by itself and in combination with endocrine and targeted therapies. Researchers will initially focus on safety and dosing, while also looking for early signs that the drug is actually shrinking or controlling tumors.

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Prelude also has enough money to get the program moving. The company finished June with approximately $155 million in cash, cash equivalents, restricted cash and marketable securities, which management expects will fund operations into the second quarter of 2028.

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There's obviously a long way to go here. PRT13722 hasn't been tested in humans yet, and most drugs entering Phase 1 never reach the market.

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But FDA clearance removes the first regulatory hurdle and gives Prelude a chance to find out whether its selective approach to KAT6A can deliver the same cancer-fighting potential without some of the toxicity associated with broader KAT6 inhibitors.

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For a small biotech, that's certainly worth watching.

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