Filed pursuant to Rule 424(b)(3)

Registration Statement No. 333-262339


Prospectus Supplement No. 12

(To Prospectus dated March 21, 2022)

eFFECTOR Therapeutics, Inc.



This prospectus supplement updates, amends and supplements the prospectus dated March 21, 2022 (the “Prospectus”), which forms a part of our Registration Statement on Form S-1 (Registration No. 333-262339). Capitalized terms used in this prospectus supplement and not otherwise defined herein have the meanings specified in the Prospectus.

This prospectus supplement is being filed to update, amend and supplement the information included in the Prospectus with the information contained in our Current Report on Form 8-K (the “Current Report”), filed with the SEC on October 26, 2022. Accordingly, we have attached the Current Report to this prospectus supplement.

This prospectus supplement is not complete without the Prospectus. This prospectus supplement should be read in conjunction with the Prospectus, which is to be delivered with this prospectus supplement, and is qualified by reference thereto, except to the extent that the information in this prospectus supplement updates or supersedes the information contained in the Prospectus.

Our common stock and warrants are listed on the Nasdaq Capital Market under the symbols “EFTR” and “EFTRW.” On October 25, 2022, the closing price of our common stock was $0.5846 and the closing price of our warrants was $0.1432.

We are an “emerging growth company” under federal securities laws and are subject to reduced public company reporting requirements. Investing in our securities involves certain risks. See “Risk Factors” beginning on page 7 of the Prospectus.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if the Prospectus or this prospectus supplement is truthful or complete. Any representation to the contrary is a criminal offense.

The date of this prospectus supplement is October 26, 2022.




Washington, D.C. 20549







Date of Report (Date of earliest event reported): October 26, 2022


eFFECTOR Therapeutics, Inc.

(Exact name of registrant as specified in its charter)



(State or other jurisdiction
of incorporation)


File Number)


(I.R.S. Employer
Identification No.)


142 North Cedros Avenue, Suite B

Solana Beach, California


(Address of principal executive offices)

(Zip Code)


(858) 925-8215

(Registrants telephone number, including area code)


(Former name or former address, if changed since last report)


Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:



Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)



Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)



Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))



Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))


Securities registered pursuant to Section 12(b) of the Act:

Title of each class


Trading Symbol(s)


Name of each exchange
on which registered

Common stock, $0.0001 par value per share




Nasdaq Capital Market

Warrants to purchase common stock




Nasdaq Capital Market


Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (Sec.230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (Sec.240.12b-2 of this chapter).


Emerging growth company


If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.




Item 8.01 Other Events.


On October 26, 2022, eFFECTOR Therapeutics, Inc. (the “Company”) announced that it has completed enrollment for the second cohort of a three cohort Phase 1b clinical trial of zotatifin in non-hospitalized adults with confirmed COVID-19 infection. The Company anticipates opening enrollment in the third cohort by the end of 2022, and expects to report topline data for all three cohorts in the first half of 2023.


The study is a double-blind, randomized, placebo-controlled trial evaluating the safety and antiviral activity of a single dose of zotatifin and is being conducted in collaboration with the Quantitative Biosciences Institute (QBI) at the University of California, San Francisco, which holds a $5 million cooperative agreement sponsored by the Defense Advanced Research Projects Agency.


Forward-Looking Statements


eFFECTOR cautions you that statements contained in this current report regarding matters that are not historical facts are forward-looking statements. The forward-looking statements are based on our current beliefs and expectations and include, but are not limited to, statements regarding: the future clinical development of zotatifin, including expectations on enrollment and the timing of reporting data from an ongoing clinical trial. Actual results may differ from those set forth in this current report due to the risks and uncertainties inherent in our business, including, without limitation: interim results of a clinical trial are not necessarily indicative of final results and one or more of the clinical outcomes may materially change as patient enrollment continues, following more comprehensive reviews of the data and as more patient data become available; and other risks described in our prior filings with the Securities and Exchange Commission. You are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date hereof, and we undertake no obligation to update such statements to reflect events that occur or circumstances that exist after the date hereof. All forward-looking statements are qualified in their entirety by this cautionary statement, which is made under the safe harbor provisions of the Private Securities Litigation Reform Act of 1995.






Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.



eFFECTOR Therapeutics, Inc.




Date: October 26, 2022


/s/ Michael Byrnes



Michael Byrnes



Chief Financial Officer