$125,000,000

Common Stock

We have entered into a sales agreement with TD Securities (USA) LLC ("TD Cowen") relating to shares of our common stock 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 $125,000,000 from time to time through or to TD Cowen acting as our agent or principal.

Our common stock is listed on The Nasdaq Global Select Market under the symbol "ALEC." On May 6, 2026, the last reported sale price of our common stock was $2.57 per share.

Sales of our common stock, if any, under this prospectus supplement and the accompanying prospectus will be made in negotiated transactions, including block trades or block sales, or by any method permitted by law deemed to be an "at the market offering" as defined in Rule 415 promulgated under the Securities Act of 1933, as amended (the "Securities Act"), including without limitation sales made through the Nasdaq Global Select Market or on any other trading market for our common stock, or by any other method permitted by law. TD Cowen is not required to sell any specific amount of securities, but will act as our sales agent using commercially reasonable efforts consistent with its normal trading and sales practices, on mutually agreed terms between TD Cowen and us. There is no arrangement for funds to be received in any escrow, trust, or similar arrangement.

The compensation to TD Cowen for sales of common stock sold pursuant to the sales agreement will be an amount up to 3.0% of the gross proceeds of any shares of common stock sold under the sales agreement. In connection with the sale of the common stock on our behalf, TD Cowen may be deemed to be an "underwriter" within the meaning of the Securities Act, and the compensation of TD Cowen may be deemed to be underwriting commissions or discounts. We have also agreed to provide indemnification and contribution to TD Cowen with respect to certain liabilities, including liabilities under the Securities Act or the Securities Exchange Act of 1934, as amended (the "Exchange Act").