The Biotech That Raised $670 Million Before It Even Has a Phase 3 Trial
Parabilis Medicines just priced a $670 million IPO, the second-largest biotech debut in U.S. history, and it doesn't even have a Phase 3 trial yet. Backed by a $75 million Regeneron co-sign and a platform that targets "undruggable" cancer proteins, this is either the smartest bet in oncology or the most expensive leap of faith.
A Shower Curtain, a Borrowed Lab, and $670 Million
In 2016, a Harvard chemist named Gregory Verdine and his co-founder WeiQing Zhou set up shop in a rented corner of a Newton, Massachusetts lab. Their equipment was mostly secondhand. Their most expensive instrument was shielded from the elements by an $8 floral shower curtain from a big-box store.
A decade later, the company they built just priced the largest biotech IPO in U.S. history.
Parabilis Medicines (formerly FogPharma) sold 33.5 million shares at $20 apiece on Nasdaq, raising roughly $670 million before fees. Regeneron bought another $75 million worth of stock in a concurrent private placement. Add in the underwriters' option to purchase 5 million more shares, and the total capital raised from this listing could stretch past $845 million.
For context, Moderna's famous 2018 IPO raised about $600 million. Kailera Therapeutics grabbed $625 million last year.
So what exactly did investors just throw three-quarters of a billion dollars at?
A Drug Platform That Picks Locks Nobody Else Can
Parabilis is built around something called Helicon peptides: tiny, specially designed protein fragments that can slip inside a cell and grab onto targets that traditional drugs can't reach. Think of it like this: most drugs work by blocking receptors on the outside of a cell, like sticking gum in a keyhole. Helicons actually get through the door and mess with the machinery inside.
That matters because some of the most important cancer-driving proteins live inside cells, where antibodies and small molecules struggle to operate. The company's lead candidate, zolucatetide, targets a protein called β-catenin (beta-catenin) that fuels several hard-to-treat cancers, including desmoid tumors, liver cancer, and colorectal cancer.
Zolucatetide is currently in a Phase 1/2 trial, testing safety and early signs of activity in patients with advanced solid tumors. A registrational Phase 3 study in desmoid tumors is expected to begin in the first half of 2027.
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Behind that lead program sit two preclinical assets targeting prostate cancer (an ERG degrader and an AR-ON degrader), plus plans for additional Helicon-based drugs down the line. It's a platform story, not a one-trick pony.
Why Regeneron Wrote a $75 Million Check at a 10% Discount
Regeneron didn't just show up to the IPO like a regular investor. It negotiated a private placement at $18 per share, a 10% discount to the public offering price, as part of a broader strategic deal announced in May 2026.
That deal is a research collaboration focused on Antibody-Helicon Conjugates (AHCs): imagine stitching Parabilis's cell-penetrating Helicon peptides onto Regeneron's world-class antibodies. If traditional antibody-drug conjugates (ADCs) are guided missiles with a chemical warhead, AHCs would be guided missiles carrying a key that unlocks previously untouchable targets inside cancer cells.
The collaboration covers five initial targets and could be worth up to approximately $2.3 billion in total, including upfront payments, equity, development, regulatory, and commercial milestones, plus tiered royalties. The $75 million equity stake gives Regeneron skin in the game at the company level, not just the program level. It's the difference between betting on one horse and buying a piece of the stable.
From Parabilis's perspective, having Regeneron's name on the cap table served as a massive credibility stamp. Large pharma companies don't typically cut checks into firms they expect to stumble. That signal helped the IPO upsize from an initial target of roughly $450 to $475 million all the way to $670 million.
The IPO Window Is Open, but Only for the Right Guests
Parabilis's blockbuster listing didn't happen in a vacuum. The 2026 biotech IPO market is best described as "open but picky." Analysts and bankers at BIO 2026 said they expect up to a dozen biotech IPOs in Q3 alone, provided macro conditions cooperate. But the deals clearing the bar share a common profile: late-stage (or near-late-stage) programs, differentiated science, and disciplined pricing.
The bar is especially high because big pharma M&A remains fierce competition for the best assets. More large biopharma deals (in the $5 to $15 billion range) have closed in 2026 than in all of 2025. Companies that might have gone public a few years ago are instead getting acquired before they ever ring the Nasdaq bell.
Parabilis threaded the needle by combining a novel platform, a big pharma co-sign, and an oncology focus in indications with serious unmet need. Investors treated it like a rare collectible rather than another biotech with a PowerPoint full of preclinical mice data.
The Elephant in the Room: No Phase 3, Lots of Faith
Let's be honest about the tension here. Parabilis does not have a Phase 3 trial running. It does not have a marketed drug. Zolucatetide is still in Phase 1/2, and the registrational study won't start until 2027 at the earliest. The company's other programs haven't even filed for permission to test in humans yet.
So $670 million (plus the Regeneron placement, plus greenshoe potential) is a staggering amount of capital for a company whose most advanced asset is still in early clinical testing. That's like paying superstar money for a rookie who looked great in preseason but hasn't played a regular-season game.
The counterargument: Parabilis has spent roughly $600 million of its $800-plus million in private funding on R&D, building out a 120,000-square-foot facility and a deep discovery engine. CEO Mathai Mammen, the former global R&D chief at Johnson & Johnson who took the helm in 2023, brings the kind of operational credibility that institutional investors crave. The board reads like a biotech all-star roster, featuring names like Alexis Borisy and Rick Klausner (founder of Altos Labs).
And the proceeds have a clear destination: fund the Phase 3 desmoid tumor trial, push the ERG and AR-ON programs into the clinic, and keep expanding the Helicon platform.
What to Watch Next
The first real test comes when Parabilis reports clinical data from the Phase 1/2 trial of zolucatetide. Response rates, durability, and safety in desmoid tumors will either validate the platform thesis or send investors scrambling for the exits.
After that, the Phase 3 launch in early 2027 becomes the next major catalyst. If zolucatetide delivers in a registrational setting, the Helicon platform suddenly looks like one of the most exciting new modalities in oncology. If it stumbles, $670 million worth of investor optimism will evaporate fast.
For now, Parabilis has the cash, the team, and the pharma partner to take a legitimate shot. The shower curtain days are definitely over.
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