Dresner v. Silverback Therapeutics Inc

District Court, W.D. Washington·Decided November 4, 2022·No. 2:21-cv-01499·Unknown

Opinion

UNITED STATES DISTRICT COURT WESTERN DISTRICT OF WASHINGTON AT SEATTLE BENJAMIN DRESNER, individually CASE NO. C21-1499 MJP and on behalf of all others similarly situated, ORDER ON MOTION TO DISMISS Plaintiff, v. INC., LAURA K. SHAWVER, HAWKINSON, PETER THOMPSON, HERSHBERG, SAQIB ISLAM, ROOT, THILO SCHROEDER, and Defendants. This matter comes before the Court on Defendants’ Motion to Dismiss (Dkt. No. 34). The Court, having reviewed the Motion, Plaintiffs’ Opposition (Dkt. No. 37), the Reply (Dkt. No. 38), and all supporting materials and documents, GRANTS the Motion. Plaintiffs bring this case as a potential class action alleging negligence and securities fraud based on the premise that Silverback, and the individually named Defendants, knew or should have known that their developmental drug was not safe or effective as an anti-tumor drug.

Therefore, the filings with the Securities and Exchange Commission (“SEC”), press releases and other reports made by Defendants were false and misled investors. Silverback Therapeutics is a biopharmaceutical company that seeks to develop treatments for cancer, chronic viral infections, and other serious diseases that express a protein called HER2. (First. Am. Compl. (“FAC”) ¶ 37 (Dkt. No. 29): Mot. to Dismiss (“Motion”) at 3 (Dkt. No. 34).) Silverback developed its lead drug candidate, SBT6050, as a novel treatment for these diseases. (Motion at 3.) SBT6050 is an Antibody-Drug Conjugate that targets tumors, such as breast, gastric, and non-small cell lung cancers. (FAC ¶ 38.) The drug is designed to activate myeloid cells, a class of immune cells that can make up to 10% of the cells in a tumor, and in doing so, promote direct tumor killing and recruitment of other immune cells that can also have

tumor killing properties. (Motion at 4.) In order for SBT6050 to be sold commercially, it must first undergo a clinical trial involving three phases of human testing. Phase 1 trials are designed to determine the pharmacologic actions of the drug in humans, the side effects associated with increasing doses, and “if possible, to gain early evidence on effectiveness.” 21 C.F.R. § 312.21. This case arises out of Silverback’s disclosures surrounding the Phase 1 testing of SBT6050. A. SBT6050 Phase 1 Clinical Trial and Silverback’s Initial Public Offering In July 2020, Silverback began a Phase 1 clinical trial that would “monitor key [pharmacodynamic (“PD”)] biomarkers in both the blood and the tumor which have been

associated with tumor regression in [the] preclinical mouse studies and was observed in [the] preclinical NHP [non-human primate] studies.” (FAC ¶ 42.) The trial would evaluate biomarkers of immune cell activation and anti-tumor activity of SBT6050 in patients that have failed all other available therapies, as well as test the safety and tolerability of SBT6050. (Id.; Declaration

of Koji Fukumura, Exhibit A at 3 (Dkt. No. 34-30).) Phase 1 of the trial was broken up into four different parts. Part 1 involved SBT6050 monotherapy dose-escalation and expansion. (FAC ¶ 1.) Part 2 focused on monotherapy dose expansion in tumor-specific cohorts. (Id.) Part 3 tested pembrolizumab (a type of cancer drug) combination dose-escalation. (Id.) And Part 4 looked at a pembrolizumab combination dose expansion cohort. (Id.) In Part 1 of Phase 1, which began in July 2020, Silverback enrolled six patients and administered SBT6050 every two weeks at 0.3 mg/kg each dose. (Fukumura Decl. Ex. A at 130.) Five months into Part 1 of the Phase 1 trial, on December 3, 2020, Silverback issued common stock that began trading publicly at $21.00 per share. (FAC ¶¶ 4- 5.) At the same time Silverback filed a registration statement and a prospectus with the SEC. (FAC ¶¶ 3-4.) Plaintiffs

refer to these documents as the “Offering Documents.” (FAC ¶ 4.) Plaintiffs allege the Offering Documents were negligently prepared, contained untrue statements of material fact or omitted facts necessary to make the statements not misleading, and were not prepared in accordance with the rules and regulations governing their preparation. (FAC ¶ 5.) The December 2020 Offering Documents stated, among other things, that thus far in the trial, Silverback observed changes in pharmacodynamic markers in the first dose cohort and anticipated providing an update on the interim data from the Phase 1 dose-escalation cohorts in the second half of 2021. (FAC ¶ 47.) The Offering Documents also discussed the adverse events (side effects) seen thus far in the clinical patients, as well as risk factors investors should be

aware of, and Silverback’s beliefs and goals for SBT6050’s marketability. (FAC ¶¶ 47-52; Fukumura Decl. Exs. A, B, C, and D.) The First Amended Complaint highlights certain portions of the Offering Documents’ statements of marketability, in particular Silverback’s statements that the drug had been designed differently from other anti-tumor drugs, meaning that it could be

used in combination with other drugs that are otherwise not typically available for combination treatment. (FAC ¶¶ 50-51.) Silverback believed that, ideally, this would allow the drug to be used in early-line standard of care regiments. (Id.) B. Silverback’s Statements from March 2021 – August 2021 Silverback issued and filed with the SEC its first annual report to investors on March 29, 2021. (FAC ¶ 55.) Much of the report contained information previously disclosed in the Offering Documents. (FAC ¶¶ 55-58.) For instance, the March filing contained the same paragraphs explaining how SBT6050 differed from other anti-tumor drugs, that Silverback anticipated providing an update on the interim data from Phase 1 single agent dose-escalation cohorts in the second half of 2021, and that Silverback had observed changes in patients’ pharmacodynamic

markers in the first dost cohort. (FAC ¶¶ 55-60) The filing also stated that investors could expect an update from Phase 1, SBT6050 plus pembrolizumab combination, in the first half of 2022, and that enrolled treatment had been initiated in Part 3 of the Phase 1 study. (Fukumura Decl. Ex. E at 24.) At the same time, Silverback issued a press release, which stated in the pertinent part: 2020 was an extraordinary year for Silverback, with the initiation of our first clinical study for SBT6050, in which pharmacological activity was observed in the first dose cohort, the advancement of each of our preclinical programs, expansion of our strong team, and the successful closing of our IPO in December. . . (FAC ¶ 62.) The press release further stated that “[c]hanges in pharmacodynamic markers consistent with potential mechanism of action have been observed in patients treated in the first monotherapy dose cohort.” (Id.) Silverback again reported to investors in May and August of 2021, when it filed its first

and second quarterly reports for 2021 with the SEC. (FAC ¶¶ 64, 67.) Silverback’s May report stated that SBT6050 “continues to advance through monotherapy and pembrolizumab combination dose escalation arms of the Phase 1/1b clinical study” and that it was “on track to deliver interim clinical data from the monotherapy dose escalation arm of the study in the second half of 2021.” (FAC ¶ 65.) In August, Silverback issued a press release along with its quarterly filing. (FAC ¶ 67.) The press release stated that Silverback had “observed pharmacodynamic markers in the first monotherapy dose cohort” and that the trial was progressing with “continued robust enrollment.” (Id.) Each time Silverback issued a report or statement, it disclosed that the statements contain “certain forward-looking statements that involved risks and uncertainties that could cause actual

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Dresner v. Silverback Therapeutics Inc, (W.D. Wash. 2022).

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