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Nippon Shinyaku exercises USD 30 million option for AB2 Bio's rare disease biologic

Edited by Robert McTiernan··3 min read
Nippon Shinyaku exercises USD 30 million option for AB2 Bio's rare disease biologic

Japan-based Nippon Shinyaku Co., Ltd. (TSE: 4516) has exercised its option to acquire exclusive US commercialization rights to tadekinig alfa, Switzerland-based AB2 Bio Ltd.'s recombinant human interleukin-18 binding protein, paying USD 30 million to convert an 18-month option into a full commercialization license. The exercise follows positive interactions with the US FDA and positions Nippon Shinyaku's US subsidiary, NS Pharma, Inc., to launch the biologic in the treatment of monogenic IL-18-driven hyperinflammatory syndrome caused by NLRC4 and XIAP mutations — two ultra-rare pediatric conditions with no currently approved therapies.

The option was originally signed in January 2025 for an initial payment of USD 6 million, with up to USD 30 million in additional early payments during the option period — bringing aggregate pre-exercise cash to AB2 Bio to up to USD 36 million. The full deal structure carries up to USD 100 million in development milestones and a combined USD 500 million pool of commercial milestones and royalties, for a total potential value of up to approximately USD 636 million. AB2 Bio retains all rights outside the US, including in Europe where tadekinig alfa holds EU Orphan Drug designation, preserving optionality for a future European licensing transaction.

Tadekinig alfa is a recombinant form of the naturally occurring IL-18 binding protein, functioning as a decoy receptor that sequesters free IL-18 and blocks its pro-inflammatory signaling. The asset holds Breakthrough Therapy, Orphan Drug, and Rare Pediatric Disease designations from the US FDA. The designation also makes the program eligible for a Priority Review Voucher upon approval, creating an additional potential source of value.

The option exercise followed regulatory interactions rather than the release of new clinical data, suggesting Nippon Shinyaku viewed the regulatory pathway as sufficiently advanced to justify converting the option into a commercialization license.

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The agreement extends a series of rare disease commercialization partnerships Nippon Shinyaku has built through NS Pharma. In June 2026, the company secured an option to commercialize Elixirgen Therapeutics' Duchenne muscular dystrophy (DMD) mRNA therapy EXG-7001 in the US under a similar structure, while NS Pharma is preparing for the potential US launch of Capricor Therapeutics' deramiocel ahead of its August 22, 2026 PDUFA date. Nippon Shinyaku also holds US and Asia rights to REGENXBIO's gene therapies RGX-121 and RGX-111, reinforcing its strategy of building a rare disease portfolio through commercialization-focused partnerships.

Across these transactions, Nippon Shinyaku consistently licenses commercialization-only rights, leaving manufacturing and regulatory responsibility with the originator. AB2 Bio retains BLA preparation and US regulatory activities under the tadekinig alfa agreement, consistent with that playbook. The approach allows Nippon Shinyaku to build out NS Pharma's rare disease commercial infrastructure without assuming development-stage risk, while the USD 30 million exercise payment for a US-only, pre-approval, ultra-rare asset sits at the upper end of comparable single-territory licenses — a premium likely reflecting the triple FDA designation stack and the embedded PRV optionality.

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