Filed Pursuant to Rule 424(b)(5)
Registration No. 333-272088
PROSPECTUS SUPPLEMENT
(To Prospectus dated May 19, 2023)
$500,000,000

Common Stock
We have entered into a sales agreement (the “Sales Agreement”) with Leerink Partners LLC (“Leerink Partners”) dated February 22, 2024, relating to shares of our common stock, par value $0.01 per share, offered by this prospectus supplement and the accompanying prospectus. In accordance with the terms of the Sales Agreement, we may offer and sell shares of our common stock having an aggregate offering price of up to $500.0 million from time to time through Leerink Partners, acting as our agent.
Our common stock is listed on the Nasdaq Global Select Market under the symbol “INSM”. The last reported sale price of our common stock on the Nasdaq Global Select Market on February 21, 2024 was $28.24 per share.
Sales of our common stock, if any, under this prospectus supplement and the accompanying prospectus will be made in sales deemed to be “at the market offerings” as defined in Rule 415 promulgated under the Securities Act of 1933, as amended (the “Securities Act”). Leerink Partners is not required to sell any specific number or dollar amount of shares of our common stock, but will act as our sales agent using commercially reasonable efforts consistent with its normal trading and sales practices, or mutually agreed terms between Leerink Partners and us. There is no arrangement for funds to be received in any escrow, trust or similar arrangement.
The compensation payable to Leerink Partners for sales of common stock pursuant to the Sales Agreement will be an amount equal to 3.0% of the gross proceeds of any shares of common stock sold under the Sales Agreement. See “Plan of Distribution” beginning on page S-13 for additional information regarding the compensation to be paid to Leerink Partners. In connection with the sale of the common stock on our behalf, Leerink Partners will be deemed to be an “underwriter” within the meaning of the Securities Act and the compensation paid to Leerink Partners will be deemed to be underwriting commissions or discounts. We have agreed in the Sales Agreement to provide indemnification and contribution to Leerink Partners with respect to certain liabilities, including liabilities under the Securities Act and the Securities Exchange Act of 1934, as amended (the “Exchange Act”).
Investing in our common stock involves a high degree of risk. You should carefully consider the risks described under the heading “Risk Factors” beginning on page S-8 of this prospectus supplement and the documents incorporated by reference into this prospectus supplement.
Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.
Leerink Partners
Prospectus Supplement dated February 22, 2024
