Parabilis Medicines, formerly FogPharma, is an oncology biotech built on Helicon peptides: stabilized alpha-helical peptides engineered to drug intracellular targets that resist small molecules and antibodies. Its lead asset, zolucatetide, blocks beta-catenin, the central effector of Wnt signaling, and posted a 74% objective response rate in a 19-patient desmoid-tumor cohort in the data behind its public filings.
The company moved fast in 2026. In May it signed a collaboration with Regeneron worth up to $2.3 billion, a $75 million upfront equity investment plus milestones across five targets, to develop antibody-helicon conjugates pairing the Helicon payload with Regeneron antibodies. On June 4 it priced a Nasdaq IPO (ticker PBLS) at $17-19 per share with a $476 million target; on June 10 it upsized and priced 33.5 million shares at $20, raising $670 million and setting the venture-backed biotech IPO record. Shares opened at $33.35 and closed at $31.60 on debut, a 58% first-day gain. Proceeds fund zolucatetide through Phase 3 in desmoid tumors (planned H1 2027) and into familial adenomatous polyposis and hepatocellular carcinoma.
Stories here cover zolucatetide trial readouts, the Helicon platform, and the Regeneron partnership. See [[zolucatetide]], [[helical-peptide]], and [[desmoid-tumors]] for adjacent threads.
Parabilis Medicines (Nasdaq: PBLS) opened June 10 at $33.35 and closed at $31.60 on its Nasdaq debut, a 58% first-day gain after pricing an upsized $670 million IPO at $20 per share — above the previously announced $17-19 range and well past the $476 million initial target Parabilis set on June 4. The 33.5 million-share offering breaks the venture-backed biotech IPO record. Proceeds extend runway for the lead asset zolucatetide, a cell-penetrating helical peptide targeting Wnt/β-catenin in cancer, with a Phase 3 in desmoid tumors expected in the first half of 2027.
Parabilis Medicines (formerly FogPharma) set terms June 4 for a Nasdaq IPO under ticker PBLS: 25 million shares at $17-19, raising about $413 million, or up to $476 million if underwriters exercise the overallotment. Proceeds fund its lead asset zolucatetide, a cell-penetrating helical peptide that blocks beta-catenin, through dose expansion and into Phase 3 for desmoid tumors, plus studies in familial adenomatous polyposis and hepatocellular carcinoma. The offering follows a $75 million Regeneron investment tied to a collaboration worth up to $2.3 billion for antibody-helicon conjugates.
Regeneron Pharmaceuticals and Parabilis Medicines announced May 18 a strategic research collaboration to discover and develop antibody-Helicon conjugates (AHCs) — a novel modality combining Regeneron's antibody platform with Parabilis's Helicon stabilized helical peptide technology. Deal structure: $50M upfront, $75M equity commitment, and up to $2.2B in development and regulatory milestones across an initial five targets, plus tiered royalties. The Helicon platform locks peptides into their bioactive helical conformation, enabling targeting of historically undruggable protein-protein interaction surfaces that small molecules cannot access. The conjugate format pairs antibody-mediated tissue homing with peptide payload delivery — an extension of the broader peptide-drug-conjugate field that included Bicycle Therapeutics' bicyclic peptide-MMAE conjugates and Avacta's FAP-activated PDCs. The deal is the largest single peptide-platform partnership announced in 2026.
Parabilis Medicines (formerly FogPharma) filed its S-1 on May 19 to list on Nasdaq under ticker PBLS, seeking ~$100M to fund Phase 3 of zolucatetide (FOG-001), a stabilized helical peptide and the first direct inhibitor of the β-catenin:TCF interaction. As of February 16, 38 desmoid-tumor patients were dosed; 25 had sufficient follow-up to be response-evaluable, all showed tumor reduction, and 74% of the 19 patients with ≥2 post-baseline scans hit RECIST 1.1 objective response. The IPO follows a $305M Series F in January and a Regeneron research deal worth up to $2B. FDA granted fast track designation for desmoid tumors.