A Peptide Company Just Set the Record for the Largest Venture-Backed Biotech IPO

Parabilis Medicines, the Cambridge, Massachusetts company formerly known as FogPharma, has closed the largest initial public offering ever for a venture-backed biotech, a milestone announced June 11 that places a peptide platform atop a list long dominated by antibody and small-molecule firms.

The numbers come with a wrinkle worth getting right. Parabilis priced its shares at $20.00 on June 9 and began trading on the Nasdaq Global Select Market under the ticker PBLS on June 10. BioPharma Dive reported the offering at $670 million, the base 33.5-million-share deal as priced. When underwriters then fully exercised their option to buy an additional 5,025,000 shares, the upsized deal totaled 38,525,000 shares for gross proceeds of $770.5 million, per the company’s closing announcement. In a concurrent private placement that settled the same day, Regeneron Pharmaceuticals, a new research partner, purchased roughly $75 million of stock at $18.00 per share, 90% of the IPO price. Parabilis says it has now raised more than $1.2 billion in 2026 across public offerings, private financing, and collaborations.

Either figure clears the prior records. The raise eclipses Moderna’s $604 million offering in 2018 and Kailera’s $625 million earlier this year to become the largest venture-backed biotech IPO on record.

What Parabilis is selling is, at bottom, a chemistry. Its Helicons are stabilized helical peptides, engineered to lock into the shape of an alpha helix so they can enter cells and grip protein surfaces that antibodies (too large to cross the cell membrane) and small molecules (too small to cover a broad target) have struggled to reach. The company describes the platform as a route to proteins “that have long been beyond the reach of conventional medicines.”

Its most advanced candidate, zolucatetide, targets the beta-catenin pathway. Per BioPharma Dive, Parabilis has reported early signals in desmoid tumors, a type of noncancerous but locally aggressive soft-tissue growth, and plans to begin a Phase 3 trial in that setting in the first half of 2027, alongside testing in other cancers and an inherited polyposis condition. The company was founded by serial biotech entrepreneur Gregory Verdine and is led by chief executive Mathai Mammen, formerly of Johnson & Johnson.

For a field most often introduced to the public through weight-loss headlines, the Parabilis debut is a different kind of proof point: record capital placed on peptides as intracellular drugs aimed at oncology rather than metabolism. Whether the chemistry becomes medicine is a question for the clinic, since zolucatetide has not yet reported Phase 3 results, but the capital markets have already rendered an unusually emphatic early verdict.