Seaport, Hemab File IPO Papers as Kailera Prices—Biotech Window Cracks Open

Seaport and Hemab filed S-1 registration statements with the SEC this week while Kailera completed pricing on its public offering, marking the first sustained cluster of biotech IPO activity since early 2023. Kailera priced $75 million in its debut, according to preliminary filings, while Seaport and Hemab disclosed deal sizes of approximately $100 million and $80 million respectively in their initial paperwork. The three names represent different therapeutic categories—oncology, rare disease, and immunology—suggesting syndicate desks are testing breadth, not backing a single thesis.

The filings arrive after biotech IPO proceeds fell 82% year-over-year in 2024, with total capital raised dropping to $2.1 billion from $11.7 billion in 2023. Median time from filing to pricing stretched to 147 days in the second half of last year, compared to 63 days in 2021. Seaport's filing indicates the company burned $34 million in cash during its most recent fiscal year and holds $62 million on the balance sheet, implying roughly 18 months of runway at current spend. Hemab reported similar metrics: $28 million annual burn, $71 million in cash. Both are pre-revenue, Phase 2 assets. Kailera, by contrast, carries partnership revenue from a Tier 1 pharma—$19 million trailing twelve months—and guided to breakeven by mid-2026 in roadshow materials.

The timing reflects two structural shifts. First, the XBI biotech ETF climbed 11% since November, outpacing the Russell 2000 by 400 basis points and signaling rotation into speculative growth. Second, the FDA approved 12 novel therapies in Q4 2024, the strongest quarterly pace since Q2 2021, renewing conviction that clinical pipelines can still convert. Crossover funds that sat out 2023 and 2024 are beginning to allocate again—Casdin Capital and RA Capital participated in Kailera's private placement that preceded the IPO, and both typically anchor follow-on public rounds. That pattern matters because biotech issuers rely on repeat capital more than most sectors; 63% of companies that went public between 2018 and 2022 returned for secondary offerings within 24 months. If this cohort can price near the midpoint and hold, the follow-on calendar for late 2025 and early 2026 expands materially.

Allocators should watch three near-term catalysts. Seaport is expected to price during the week of March 10, assuming roadshow momentum holds and the syndicate—led by Jefferies and Leerink—can place the deal without heavy discounting. Hemab's timeline appears slightly longer, with pricing likely in late March or early April given additional SEC comment rounds still pending. More importantly, Kailera's first-day trading performance will set the tone; if shares close above the $12 IPO price and hold for five sessions, it signals real demand beyond anchor allocations. A break below $10.50 would likely stall the pipeline and push other filers into extended roadshows or delayed pricing. The next six weeks will clarify whether this is a genuine reopening or a small batch that exhausts available capital.

Between now and mid-April, 17 additional biotech companies are in various stages of confidential IPO review, according to tracking from Renaissance Capital. If three can price cleanly, that number accelerates. If one breaks badly, the window closes again and those 17 names retreat to private markets where crossover funds are already stretched. The February filings are not predictions—they are tests.