13.        Intangible assets and goodwill

Definite-lived intangibles

Definite-lived intangible assets consisted of the following at September 30, 2026 and December 31, 2025:

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Akcea is entitled to receive royalty payments subject to certain terms set forth in the Tegsedi-Waylivra Agreement related to sales of Waylivra and Tegsedi. In accordance with the guidance for an asset acquisition, the Company records royalty payments when they become payable to Akcea and increases the cost basis for the Waylivra and Tegsedi intangible assets.

For the nine months ended September 30, 2026, royalties of $4.3 million and $3.4 million related to Tegsedi and Waylivra, respectively, were recorded on the consolidated balance sheet within intangible assets, net. As of September 30, 2026, a royalty payable of $1.1 million and $0.5 million for Tegsedi and Waylivra, respectively, was recorded on the consolidated balance sheet within accounts payable and accrued expenses.

As of the three months ended June 30, 2026, aggregate Sephience global net sales in the prior four consecutive quarters exceeded $250.0 million, which, pursuant to the Censa Merger Agreement, triggered a $30.0 million net sales milestone payment to the former Censa securityholders. The $30.0 million milestone was recorded in accounts payable and accrued expenses and intangible assets on the consolidated balance sheet as of September 30, 2026. As of the three months ended September 30, 2026, aggregate Sephience global net sales in the prior four consecutive quarters exceeded $500.0 million, which, pursuant to the Censa Merger Agreement, triggered a $50.0 million net sales milestone payment to the former Censa securityholders. The $50.0 million milestone was recorded in accounts payable and accrued expenses and intangible assets on the Company's consolidated balance sheet as of September 30, 2026. These milestones were recorded as intangible assets and are being amortized to cost of product sales over their expected useful lives on a straight-line basis.

The former Censa securityholders may also be entitled to receive other contingent payments subject to certain terms set forth in the Censa Merger Agreement related to sales of Sephience. In accordance with the guidance for an asset acquisition, the Company will record such payments when they become payable to the former Censa securityholders and increase the cost basis for the Sephience intangible asset. For the nine months ended September 30, 2026, royalties of $4.1 million were recorded for Sephience. As of September 30, 2026, a royalty payable of $3.1 million for Sephience was recorded on the consolidated balance sheet within accounts payable and accrued expenses.

For the three months ended September 30, 2026 and 2025, the Company recognized amortization expense of $12.6 million and $7.5 million, respectively, related to its intangible assets. For the nine months ended September 30, 2026 and 2025, the Company recognized amortization expense of $36.0 million and $15.4 million, respectively, related to its intangible assets.

The estimated future amortization of the Company’s intangible assets is expected to be as follows:

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The weighted average remaining amortization period of the definite-lived intangibles as of September 30, 2026 is 10.8 years.

Goodwill

As a result of the Agilis Merger on August 23, 2018, the Company recorded $82.3 million of goodwill. As of September 30, 2026, there have been no changes to the balance of goodwill since the date of the Agilis Merger. Accordingly, the goodwill balance as of September 30, 2026 is $82.3 million.