RTW Biotech Opportunities, the closed-end fund investing across public and private biotech, said BioMarin will acquire its portfolio company Alesta Therapeutics for up to $490 million.
Alesta is developing ALE1, an oral small-molecule therapy for hypophosphatasia, a rare inherited disease that impairs bone and tooth mineralisation.
BioMarin will pay $275 million upfront in cash, with up to a further $215 million contingent on milestone achievements.
Alesta will spin out its non-ALE1 assets into a new entity before close, with existing shareholders including RTW Bio retaining their pro rata stakes.
RTW Bio first backed Alesta's Series A round in December 2024 and invested again in September 2025, committing €2.4 million in total.
Its holding was valued at $3.8 million as at 31 July, representing 0.4% of the fund's net asset value (NAV).
The upfront payment implies a 41% uplift to that carrying value, adding an estimated $1.6 million, or 0.2%, to NAV.
It is the sixth acquisition from RTW Bio's portfolio announced this year, following deals involving Penumbra, RAPT Therapeutics, Apellis Pharmaceuticals, Centessa Pharmaceuticals and Apogee Therapeutics.
"BioMarin's decision to acquire the company at pre-Phase 2 data is a clear validation of our strategy of identifying and supporting differentiated science at the earliest stages of the private markets," said Rod Wong, chief investment officer of RTW Investments.
Wong pointed to large-cap pharma's cumulative $170 billion patent cliff by 2032 as a driver of continued dealmaking.
The transaction is expected to close in the third quarter.
News Intelligence what this means for the company
BioMarin is acquiring RTW Bio's portfolio company Alesta Therapeutics for up to $490 million ($275 million upfront, $215 million in milestones), marking the fund's sixth exit this year. The deal adds an estimated $1.6 million to RTW Bio's NAV—a 0.2% uplift—reflecting Alesta's tiny 0.4% weighting in the fund at 31 July; the upfront payment represents a 41% uplift to that carrying value. RTW Bio will retain pro rata stakes in Alesta's non-ALE1 assets spun into a new entity before close.
This is a modest realisation for RTW Bio—the NAV accretion is immaterial at 0.2%—but it extends a pattern of six portfolio exits announced in 2026, suggesting the fund's early-stage life sciences bets are reaching liquidity events. The deal validates RTW's strategy of backing differentiated science pre-Phase 2, though individual deal size and NAV impact remain small relative to the fund's overall portfolio.
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