Filed Pursuant to 424(b)(2)
Registration No. 333-261342
PROSPECTUS SUPPLEMENT
(To Prospectus
dated December 7, 2021)
$6,400,000
Common Stock
This prospectus
supplement and the accompanying prospectus covers the offer and sale of an additional $6,400,000 of shares of our common stock that may be offered and sold as of the date of this prospectus supplement in accordance with the terms of the amended and
restated sales agreement, or sales agreement, that we entered into on March 18, 2020 with JonesTrading Institutional Services LLC and Roth Capital Partners, LLC, or together, the Agents. Under the sales agreement, we may offer and sell shares
of our common stock having an aggregate offering price of up to $50,000,000 from time to time through or to the Agents acting as our sales agent or principal. As of the date of this prospectus supplement, we have previously sold an aggregate of
$13,168,147 of shares of our common stock pursuant to the sales agreement, and $3,675,400 of shares of common stock remain available for sale pursuant to a prospectus supplement dated December 14, 2021. We will be required to file another
prospectus supplement in the event we want to offer more shares of our common stock under the sales agreement than the $6,400,000 in shares of common stock offered by this prospectus supplement and the $3,675,400 in shares of common stock that
remain available for sale pursuant to the December 14, 2021 prospectus supplement.
Our common stock is listed on the Nasdaq Capital
Market under the symbol ACER. On May 13, 2022, the last reported sale price of our common stock on the Nasdaq Capital Market was $1.94 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 an
at the market offering as defined in Rule 415(a)(4) promulgated under the Securities Act of 1933, as amended, or the Securities Act. The Agents are not required to sell any specific amount of securities, but will act as our sales agents
using commercially reasonable efforts consistent with their normal trading and sales practices, on mutually agreed terms between the Agents and us. There is no arrangement for funds to be received in any escrow, trust or similar arrangement.
The compensation to the Agents for sales of common stock sold pursuant to the sales agreement will be an amount equal to 3.5% 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, the Agents will be deemed to be underwriters within the meaning of the Securities Act and the
compensation of the Agents will be deemed to be underwriting commissions or discounts. We have also agreed to provide indemnification and contribution to the Agents with respect to certain liabilities, including liabilities under the Securities Act
or the Securities Exchange Act of 1934, as amended.
The aggregate market value of our outstanding common equity held by non-affiliates on April 4, 2022 was $39,839,723 based on 15,310,244 shares of common stock outstanding, of which 13,105,172 were held by non-affiliates, and a closing
sale price on the Nasdaq Capital Market on such date of $3.04. During the 12 calendar months prior to and including the date hereof, we have sold $3,174,600 in shares of common stock pursuant to General Instruction I.B.6. of Form S-3.
Investing in our common stock involves risks. See the section entitled Risk Factors beginning on page S-6 of this prospectus supplement and in the documents we incorporate by reference into this prospectus supplement and the accompanying prospectus.
Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or
passed upon the adequacy or accuracy of this prospectus supplement and the accompanying prospectus. Any representation to the contrary is a criminal offense.
JonesTrading Roth Capital Partners
The date of this prospectus supplement is May 17, 2022