On September 9, 2025, the Issuer entered into a Securities Purchase Agreement (the "Purchase Agreement") with PP VII, PEF VII and certain other investors (each, an "Investor" and collectively, the "Investors"), pursuant to which the Issuer agreed to sell to the Investors, in up to two closings in the Private Placement. The initial closing of the Private Placement is anticipated to occur on or about September 11, 2025 (the "Initial Closing"), subject to customary closing conditions. At the Initial Closing, the Issuer has agreed to issue and sell 26,681,053 shares of Common Stock, at an offering price of $1.53 per share (the "Share Price") and, in lieu of Common Stock to certain Investors, pre-funded warrants to purchase 6,003,758 shares of Common Stock (the "Warrant Shares" and, together with the Common Stock, the "Securities") at an offering price of $1.5299 per pre-funded warrant (the "Pre-Funded Warrant Price"). At the Initial Closing, the Issuer will issue and sell to certain members of management, including the Issuer's CEO Josh Mandel-Brehm, the Issuer's CFO Kelly Gold, the Issuer's CMO Yuri Maricich, and the Issuer's co-founders Richard Young, who also serves as a director on the Issuer's Board of Directors (the "Board") and Leonard Zon, who serves as a Board observer, an additional 36,361 shares of Common Stock at a purchase price of $1.65 per share, for gross proceeds to the Issuer of approximately $50.1 million, before deducting placement agent fees and other expenses. Pursuant to the Purchase Agreement, subject to the occurrence of the Second Closing Trigger (defined below), the Investors have agreed to purchase at a closing (the "Second Closing") up to 32,721,172 shares of Common Stock or pre-funded warrants in lieu thereof at a purchase price per share and pre-funded warrant equal to the Share Price and the Pre-Funded Warrant Price, respectively, and members of management have agreed to an additional 39,306 shares of Common Stock at a purchase price of $1.65 per share, for gross proceeds to the Issuer of up to approximately $50.1 million. The Second Closing Trigger shall occur upon (i) the achievement of the first acceptance or clearance by a drug regulatory agency of a clinical trial application or similar filing submitted by the Issuer to commence a clinical trial in human subjects involving the administration of the Issuer's development candidate for the treatment of SYNGAP1-related disorders, or the time at which the Issuer is otherwise authorized under applicable law in such country or jurisdiction to commence such clinical trial (the "CTA Milestone"), and (ii) either (a) the achievement of a volume weighted average price per share of equal to or greater than $7.50 (subject to appropriate, proportional adjustment for any stock splits or combinations of the Common Stock occurring after the date of the Purchase Agreement) measured during any 10 consecutive trading days during the 30 trading days following the date of the Issuer's first announcement via a press release or Current Report on Form 8-K of the occurrence of the CTA Milestone (such period the "Measurement Period" and such price threshold requirement, the "Price Threshold") or (b) the Issuer's receipt of a written notice signed by the Investors holding a majority of the Securities outstanding from time to time and delivered to the Issuer during the Measurement Period that waives the Price Threshold for purposes of the Second Closing (the achievement or occurrence of (i) and (ii) are collectively, the "Second Closing Trigger"). In the event the Milestone Closing Trigger occurs as a result of a Price Threshold Waiver, only the waiving Investors will be obligated to purchase shares of Common Stock or pre-funded warrants at the Second Closing. The terms and conditions of the Private Placement are described in the Purchase Agreement, and the above summary is qualified by reference to such description and the full text of the Purchase Agreement, which is filed as Exhibit 7 to this Amendment and incorporated herein by reference. In connection with the Private Placement, the Investors entered into a Registration Rights Agreement, dated September 9, 2025, with the Issuer (the "Rights Agreement"). Pursuant to and subject to the terms of the Rights Agreement, the Issuer agreed to prepare and file to register for reseale the shares of Common Stock and the Warrant Shares underlying the pre-funded warrants issued pursuant to the Purchase Agreement. The terms and provisions of the Rights Agreement are described more fully in the Rights Agreement, and the above summary is qualified by reference to such description and the full text of the Rights Agreement, which is filed as Exhibit 8 to this Amendment and is incorporated herein by reference.

Exhibit 7: Securities Purchase Agreement, dated September 9, 2025 (filed as Exhibit 10.1 to the Issuer's Current Report on Form 8-K as filed with the Commission on September 10, 2025 (SEC File No. 001-42365) and incorporated herein by reference). Exhibit 8: Registration Rights Agreement, dated September 9, 2025 (filed as Exhibit 10.2 to the Issuer's Current Report on Form 8-K as filed with the Commission on September 10, 2025 (SEC File No. 001-42365) and incorporated herein by reference).