December 13, 2016

Cohen Milstein Sellers & Toll PLLC is conducting an investigation to determine whether ProNAi Therapeutics Inc. (“ProNAi” or the “Company”) and certain of its officers and directors made false and misleading statements and/or omissions in violation of Sections 10(b) and 20(a) of the Securities Exchange Act of 1934 or committed violations of or committed violations of Sections 11 and 15 of the Securities Act of 1933.

Class action lawsuits were filed in the U.S. District Court for the Southern District of New York and the California Superior Court by other law firms on behalf of purchasers of the common stock of ProNAi Therapeutics Inc. (NASDAQ: DNAI) between July 15, 2015 and June 6, 2016, inclusive (the “Class Period”), including those who purchased shares pursuant or traceable to the Company’s July 15, 2015 initial public offering of 8.1 million shares at $17.00 per share (“IPO”).

ProNAi’s lead product candidate is PNT2258—designed to target BCL2, a widely overexpressed oncogene linked to many forms of cancer. The complaints allege that ProNAi and certain of its officers and directors (“Defendants”) misrepresented and/or failed to disclose that: (1) two trials of PNT2258, the Wolverine and Brighton Phase 2 trials, would fail to prove the efficacy and safety of PNT2258 by failing to meet primary or secondary endpoints; and (2) because the Phase 2 trials were structured as open-label studies, ProNAi management was aware that the Wolverine study was underperforming and that patients were discontinuing participation in the Brighton study in alarming rates.

Prior to the beginning of the Class Period, ProNAi completed a Phase 1 safety trial and a Pilot Phase 2 open-label trial of PNT2258. The positive results of these trials lead ProNAi to initiate two separate Phase 2 clinical trials for different treatment populations. In December 2014, the Company initiated the Wolverine trial, an open-label 60 patient trial for the treatment of third-line relapsed or refractory diffuse large B-cell lymphoma. In October 2015, the Company initiated Brighton, an open-label 50 patient Phase 2 trial for the treatment of Richter’s transformed chronic lymphocytic leukemia. Both of these trials were ongoing during the Class Period.

On December 15, 2015, ProNAi announced that director Dr. Peter Thompson would resign from the Board of Directors and the Audit Committee effective that day. The following month, on January 26, 2016, ProNAi announced the resignation of its Chief Scientific Officer, Wendi Rodrigueza, effective February 25. On March 18, ProNAi announced the resignation of director Dr. Alvin Vitangcol, effective that day, and the decision of director Dr. Albert Chang to step down after the Company’s 2016 annual stockholders meeting. On May 2, 2016, ProNAi announced that Chief Medical Officer, Dr. Richard Messmann, notified the Company of his decision to resign on April 26, 2016.

On June 6, 2016, ProNAi issued a press release announcing interim data for the Wolverine trial. Based on these results, the Company announced that PNT2258 failed to produce sufficient efficacy results to justify its continued clinical development. In addition, ProNAi announced that 4 of the 5 patients enrolled in Brighton had already discontinued treatment. Due to underwhelming results in both trials, the Company said it was suspending all clinical development of PNT2258. The price of ProNAi stock fell from $6.38 on June 3, 2016 to $2.07 on June 6, 2016.

Cohen Milstein encourages all investors who purchased ProNAi common stock pursuant or traceable to the IPO, and/or between July 15, 2015 and June 6, 2016; or former employees with information concerning this matter to contact the firm.

If you are a ProNAi shareholder and would like to discuss your right to recover for your economic loss, you may, without any cost or obligation, call Cohen Milstein’s Managing Partner, Steven J. Toll at (888) 240-0775 or (202) 408-4600, or email him at stoll@cohenmilstein.com. If you wish to serve as lead plaintiff, you must move the Court no later than January 9, 2017, to request appointment. Any member of the proposed class may retain Cohen Milstein or other attorneys to serve as your counsel in this action, or you may do nothing and remain an absent class member.

Cohen Milstein has significant experience in prosecuting investor class actions and actions involving securities fraud, and is active in major litigation pending in federal and state courts throughout the nation. Cohen Milstein has taken a lead role in numerous important cases on behalf of defrauded investors, and has been responsible for a number of outstanding recoveries which, in the aggregate, total over two billion dollars. Prior results do not guarantee a similar outcome. For more information visit www.cohenmilstein.com.

If you have any questions about this notice or the action, or with regard to your rights, please contact either of the following:

Steven J. Toll, Esq.
Ryan Marchbank
Cohen Milstein Sellers & Toll PLLC
1100 New York Avenue, N.W.
Suite 500 East
Washington, D.C. 20005
Telephone: (888) 240-0775 or (202) 408-4600
Email: stoll@cohenmilstein.comrmarchbank@cohenmilstein.com