Dresner v. Silverback Therapeutics: the IPO class action, dismissed

Dresner v. Silverback Therapeutics: the outcome

The Silverback Therapeutics securities class action ended in a dismissal with prejudice. Dresner v. Silverback Therapeutics, Inc., No. 2:21-cv-01499, was filed on 5 November 2021 in the U.S. District Court for the Western District of Washington. On 12 April 2023 Judge Marsha J. Pechman granted the defendants' motion to dismiss the second amended class action complaint and entered judgment (docket entries 55 and 56). With prejudice means the plaintiffs may not file the same claims again in that court. As of the docket retrieved on 23 October 2026 no appeal appears, and no settlement is recorded.

The company, the IPO and the drug

Silverback was a clinical-stage biotechnology company listed on Nasdaq as SBTX. According to the law-firm summaries of the complaint, it sold 11.5 million shares at 21 dollars each in an initial public offering, with trading beginning on 3 December 2020. Its lead candidate, SBT6050, was a HER2-directed antibody linked to an immune-activating compound, being tested in a Phase 1/1b study in solid tumours.

On 13 September 2021 the company announced interim data. Plaintiffs' counsel reports that the data showed one partial response among 14 patients with HER2-positive solid tumours, and that the share price fell 4.54 dollars, more than 23 percent, to close at 14.90 dollars. That drop is the event the complaint builds on.

What the complaint alleged

The first complaint, announced by several investor firms in November 2021, asserted claims under both the Securities Act of 1933 and the Securities Exchange Act of 1934. As the firms described it, the offering documents were negligently prepared and left out that SBT6050 was less effective than the company represented, and public statements overstated the drug's clinical and commercial prospects. The notices do not list individual sentences, and the later amended complaints were not retrieved for this page.

Eleven individuals were named alongside the company in the defendants' motions to dismiss, among them Jonathan Root, Robert Hershberg and Laura K. Shawver. A person's name in a complaint is an allegation, not a finding, and the court never reached the facts.

Lead plaintiff and counsel

Two investor groups asked to run the case. Benjamin Dresner moved on 4 January 2022, the notice deadline, and Taylor and Trenton Thenhaus filed a competing motion the same day. On 23 February 2022 Judge Theresa L. Fricke granted Dresner's motion, approved Pomerantz LLP as lead counsel and Badgley Mullins Turner PLLC as liaison counsel, and denied the Thenhaus motion (entry 20). The amended complaint came due on 11 April 2022 and was filed that day.

Two rounds of motions to dismiss

Defendants moved to dismiss the amended complaint on 26 May 2022 (entry 34), and the court stayed discovery while the motion was pending. A motion hearing took place on 28 October 2022; the official transcript was filed on 5 January 2023 (entry 50). The plaintiffs then filed a second amended complaint, and the defendants moved again on 2 January 2023 (entry 47). Plaintiffs responded on 23 January, defendants replied on 27 January, and the order of dismissal with prejudice followed on 12 April.

The orders themselves were not retrieved, so the court's reasons are not summarised here. The text of entry 55 on the docket is the source for them.

Early procedure in Seattle

The case was filed by Duncan Turner of Badgley Mullins Turner, with Pomerantz lawyers Jeremy Lieberman and J. Alexander Hood admitted to appear on 12 November 2021. The court's first orders on 10 November 2021 set a joint status report, initial disclosures and discovery rules. A scheduling order of 4 March 2022 gave the plaintiffs until 11 April to amend and the defendants until 26 May to respond. When the plaintiffs and defendants missed a status-report deadline in April, the court extended it by minute order and warned that sanctions could follow. Those are routine details, but they show how little of the docket concerned the merits before the first motion to dismiss arrived.

Reading a dismissal with prejudice

Securities suits face an early test: the complaint must plead specific false statements and, for the Exchange Act claims, facts pointing to intent. Many end at that stage. The steps that came before it, notice, lead plaintiff and consolidation, follow the pattern described on the class action explainer. This case went through that sequence in about seventeen months from filing to judgment.

Other investor cases tracked here include the Eargo IPO litigation, also dismissed and affirmed on appeal, and the Revance case, which moved toward settlement after dismissal.

What stays unconfirmed

Three points remain open in the record retrieved: the final class period in the amended complaints, the reasoning of the 12 April 2023 order, and whether anyone sought review afterwards. The CourtListener docket carries entries up to number 56 for a reader who wants to check.