Erasca ERAS Securities Class Action Lawsuit Update

• Company: Erasca, Inc. (NASDAQ: ERAS)
• Lead Plaintiff Deadline: August 10, 2026
• Class Period: January 14, 2025 - April 26, 2026
• Stock Drop: April 27, 2026 - ERAS fell $2.34 (10.9%) to $19.15; April 28, 2026 - ERAS fell $9.25 (48.3%) to $9.90
• Lawsuit Type: Securities Class Action

On June 10, 2026, a securities class action complaint was filed in the United States District Court for the Southern District of California against Erasca, Inc., its co-founder and CEO Jonathan Lim, and its CFO and Chief Business Officer David Chacko. The lawsuit, captioned Cheng v. Erasca, Inc. et al., Case No. 3:26-cv-03481-AJB-JLB, alleges violations of Sections 10(b) and 20(a) of the Securities Exchange Act of 1934 on behalf of investors who purchased or otherwise acquired Erasca common stock between January 14, 2025 and April 26, 2026.

Erasca had staked its future on ERAS-0015, a pan-RAS molecular glue that the company described as a "potential best-in-class" candidate with the potential to address unmet medical needs in approximately 2.7 million patients diagnosed annually worldwide with RAS-mutant tumors. Throughout the class period, CEO Lim and other company representatives repeatedly compared ERAS-0015's preclinical performance to Revolution Medicines' RMC-6236, the leading competitor in the pan-RAS space, touting superior binding affinity, greater potency at a fraction of the dose, and preferential tumor distribution. Investors embraced the narrative. The complaint alleges that Erasca later raised approximately $258.8 million through a January 2026 common stock offering while the challenged statements remained in effect.

Then, on the morning of April 27, 2026, before the market opened, Erasca disclosed that Revolution Medicines had sent a letter alleging patent infringement and trade secret misappropriation, and demanding that Erasca cease making what RevMed called "deceptive and untrue comparative statements." Erasca stated that it believed the assertions were without merit and intended to contest them. ERAS shares slid to $19.15. That same evening, after the close, Erasca filed a second 8-K disclosing a patient death in the Phase 1 trial and acknowledging that its comparisons with RMC-6236 were based on cross-study analyses, were "not based on any head-to-head clinical trials," and were "inherently limited." By the next morning, ERAS had collapsed more than 45% in premarket trading, opening at $10.51 and closing at $9.90, as the complaint alleges that Plaintiff and other Class members suffered significant losses and damages as a result of the two-day decline.

Backdrop and Business Context

Erasca, Inc. was co-founded on July 2, 2018 in San Diego, California by Jonathan Lim, a physician-turned-biotech entrepreneur, and Kevan Shokat, a biochemist whose work on drugging the active state of RAS inspired the company's creation. The name "Erasca" is a portmanteau carrying a dual meaning: "ERAdicate RAS-driven CAncer" and "ERASe CAncer." The company commenced operations in October 2018 with about a dozen scientists recruited from Ignyta, Genentech, and Wellspring, and quickly attracted significant venture capital, closing a $42 million Series A in December 2018 and a $236 million Series B by August 2020. Erasca went public on the Nasdaq Global Select Market on July 16, 2021 at $16.00 per share, raising approximately $345 million in gross proceeds including the underwriters' overallotment option.

Erasca is a clinical-stage precision oncology company singularly focused on the RAS/MAPK signaling pathway, one of cancer's most commonly mutated cascades, which the company estimates affects roughly five million patients annually worldwide. The company has no approved products and generates no product revenue. Its pipeline centers on two clinical-stage candidates: ERAS-0015, a pan-RAS molecular glue, and ERAS-4001, a pan-KRAS inhibitor, both of which received IND clearance from the FDA in May 2025. Revolution Medicines is the most direct competitor in the pan-RAS space, with its own molecular glue, RMC-6236, further ahead in clinical development. As of March 31, 2026, Erasca held approximately $408.5 million in cash, cash equivalents, and marketable securities, with management guiding runway into the second half of 2028.

As a pre-revenue biotech, Erasca's valuation rests almost entirely on the clinical and competitive prospects of its pipeline. According to the complaint, that dependence made the company's repeated comparative claims about ERAS-0015 versus RMC-6236 central to investor decision-making, and the alleged concealment of intellectual property risks and the limitations of those comparisons all the more material.

Promises Made vs. Reality

The class period opened on January 14, 2025 at the Annual J.P. Morgan Healthcare Conference, where CEO Lim introduced ERAS-0015 as a "potential best-in-class pan-RAS molecular glue" and immediately framed it against Revolution Medicines' RMC-6236. Lim told investors that ERAS-0015 demonstrated "low sub-nanomolar to low nanomolar IC50 across multiple mutations, including wild-type" and that "what's particularly impressive is the incredibly low doses by which tumor regression is observed." He characterized the intellectual property position as "strong with exclusivity expected through 2043 and no patentability roadblocks identified to date." When a J.P. Morgan analyst pressed him about the competitive landscape, Lim acknowledged that RevMed was "clearly the trailblazer" but positioned Erasca as the natural successor, declaring that "being second in an area of high unmet need across PDAC, lung and other tumor types is a good place to be."

Two months later, in the 2024 10-K filed on March 20, 2025, Erasca deepened the comparative narrative with extensive preclinical data. The filing claimed that ERAS-0015 demonstrated "8-21-fold higher binding affinity to cyclophilin A relative to RMC-6236," showed "preferential tumor distribution and longer residence time relative to RMC-6236," and exhibited "superior in vitro potency" with "an average of 5 times greater potency" across multiple cell lines. The company stated that ERAS-0015 achieved "comparable to greater in vivo antitumor activity at doses which were approximately one-tenth to one-eighth of the dose of RMC-6236," and that in a head-to-head pharmacokinetic comparison, ERAS-0015 "outperformed RMC-6236 on three key metrics." Based on these results, Defendants predicted that "ERAS-0015 will be efficacious at lower doses than the leading pan-RAS molecular glue in development."

The comparative drumbeat intensified in January 2026. On January 12, 2026, Erasca filed a Form 8-K presentation featuring multiple slides with titles such as "ERAS-0015's higher CYPA binding affinity may be a differentiator from RMC-6236, demonstrating potential best-in-class profile" and "ERAS-0015 demonstrated significantly more potent inhibition of cell growth across KRAS mutant cell lines vs. RMC-6236." The next day, at the 2026 J.P. Morgan Healthcare Conference, Lim walked investors through the data in granular detail, explaining that ERAS-0015 achieved "the same degree of tumor regression" as RMC-6236 "with 0.3 mpk or 1/10 of the dose" and emphasizing that "6236 in this comparison requires 10x the dose." He described an insensitive lung cancer model "widely viewed as a bellwether" where ERAS-0015 again matched RMC-6236 at one-tenth the dosage. Lim characterized ERAS-0015's pharmacokinetic advantages as showing "lower clearance across the board relative to 6236, longer half-life and a higher oral bioavailability." He concluded that the early clinical signs suggested "15 has the potential to become a preferred RAS targeting backbone for combinations." On March 12, 2026, the 2025 10-K repeated the same preclinical comparison data and reported "favorable safety and tolerability results, with no dose-limiting toxicities and predominantly low-grade adverse events observed at all dose levels evaluated."

The reality, according to the complaint, was starkly different. On April 27, 2026, Erasca disclosed in a pre-market Form 8-K that Revolution Medicines' legal counsel had alleged that ERAS-0015 infringes a RevMed patent (U.S. Patent No. 12,409,225) and is connected to alleged trade secret misappropriation. RevMed also alleged that Erasca had "improperly compared preclinical data of ERAS-0015 and RMC-6236 in public disclosures" and demanded the company cease making "deceptive and untrue comparative statements." That evening, a second 8-K disclosed a patient death in the Phase 1 trial and, critically, acknowledged that the comparisons between ERAS-0015 and RMC-6236 were based on cross-study analyses, were "not based on any head-to-head clinical trials," and were "inherently limited and such data may not be directly comparable."

As alleged in the complaint, the defendants knew or recklessly disregarded that their comparative claims were improper, that Erasca faced significant patent and trade secret exposure from Revolution Medicines, and that investors were being misled about the true competitive and legal risks surrounding the company's most important drug candidate.

Timeline of Alleged Misconduct and Disclosures

Class Period: January 14, 2025 - April 26, 2026, inclusive.

January 14, 2025: Class period begins. CEO Jonathan Lim presents at the J.P. Morgan Healthcare Conference, promoting ERAS-0015 as a "potential best-in-class pan-RAS molecular glue" with detailed comparisons to Revolution Medicines' RMC-6236. Lim states IP is "strong" with "no patentability roadblocks identified to date."

March 20, 2025: Erasca files the 2024 10-K with the SEC. The filing contains extensive preclinical data comparing ERAS-0015 to RMC-6236, including claims of 8-21-fold higher binding affinity, superior in vitro potency, comparable antitumor activity at one-tenth the dose, preferential tumor distribution, and longer residence time.

May 2025: FDA clears the IND for ERAS-0015 (AURORAS-1 trial) and ERAS-4001 (BOREALIS-1 trial).

January 12, 2026: Erasca files a Form 8-K presentation with multiple slides comparing ERAS-0015 to RMC-6236, including claims of "significantly more potent inhibition of cell growth" and "comparable antitumor activity to RMC-6236 at 1/10th of the dose."

January 13, 2026: CEO Lim presents at the 2026 J.P. Morgan Healthcare Conference, providing detailed comparative data and stating that ERAS-0015 has "the potential to become a preferred RAS targeting backbone for combinations."

January 23, 2026: Erasca closes a common stock offering raising approximately $258.8 million in gross proceeds, conducted while allegedly misleading statements about ERAS-0015 were in effect.

March 12, 2026: Erasca files the 2025 10-K, repeating preclinical comparison data and reporting "favorable safety and tolerability results" with "no dose-limiting toxicities."

April 26, 2026: Class period ends.

April 27, 2026 (pre-market, 8:31 a.m. EDT): Alleged Corrective Disclosure. Erasca files a Form 8-K disclosing receipt of a letter from Revolution Medicines alleging patent infringement (U.S. Patent No. 12,409,225), trade secret misappropriation, and "improper" and "deceptive" preclinical comparisons. ERAS stock falls from $21.49 (April 24 close) to a $19.15 close on April 27.

April 27, 2026 (post-market, 4:17 p.m. EDT): Alleged Corrective Disclosure. Erasca files a second Form 8-K disclosing preliminary Phase 1 data, including a patient death involving pneumonitis that was classified as a Grade 3 TRAE and progressed to Grade 5 after withdrawal of supportive care, and acknowledging that comparisons to RMC-6236 were "not based on any head-to-head clinical trials" and were "inherently limited."

April 28, 2026: ERAS opens at $10.51 (down over 45% from April 27 close of $19.15) and closes at $9.90.

Investor Harm and Market Reaction

According to the complaint, the alleged corrective disclosures on April 27, 2026 were followed by a two-day decline in Erasca's share price. When the pre-market 8-K revealed Revolution Medicines' patent infringement and trade secret allegations on the morning of April 27, ERAS fell from its prior close of $21.49 (on April 24, the last trading day before the disclosure) to open at $20.70 and continued declining throughout the session, closing at $19.15, a loss of $2.34 per share, or approximately 10.9%.

The second wave proved far more destructive. After the close on April 27, Erasca's filing of the second 8-K, which disclosed the patient death and the company's acknowledgment that its comparisons to RMC-6236 were "inherently limited" and "not based on any head-to-head clinical trials," sent the stock into freefall in premarket trading. ERAS opened the next morning at $10.51, a decline of more than 45% from the prior close of $19.15, and continued to fall throughout the day, ultimately closing at $9.90 on April 28.

Taken together, the two-day decline from $21.49 to $9.90 represented a total loss of $11.59 per share, or approximately 53.9%, erasing hundreds of millions of dollars in shareholder value. The complaint's theory is particularly relevant to investors who purchased in the January 2026 offering or otherwise purchased during the class period while the challenged preclinical comparison narrative was in effect.

Litigation & Procedural Posture

The complaint asserts claims under Section 10(b) of the Securities Exchange Act of 1934 and Rule 10b-5 promulgated thereunder against all defendants, and under Section 20(a) of the Exchange Act against the individual defendants as controlling persons of Erasca. The defendants are Erasca, Inc., the clinical-stage oncology company; Jonathan Lim, co-founder, CEO, and Chairman of the Board; and David Chacko, CFO and Chief Business Officer

Scienter allegations center on the individual defendants' positions at the company, which gave them the power to control corporate communications and access to material non-public information regarding the true status of ERAS-0015's intellectual property risks and the propriety of its preclinical comparisons to RMC-6236.

The complaint further alleges that defendants were motivated to maintain the artificial inflation of Erasca's stock price to facilitate the January 2026 common stock offering, which raised approximately $258.8 million in gross proceeds. The timing of that offering, conducted while the allegedly misleading comparative statements were in effect, supports a strong inference of scienter according to the complaint. No insider stock sales by individual defendants are specifically alleged, and no confidential witnesses are cited.

Procedurally, the case was filed on June 10, 2026. The complaint seeks class certification on behalf of all purchasers or otherwise acquirers of Erasca common stock during the class period of January 14, 2025 through April 26, 2026, inclusive. The lead plaintiff deadline is August 10, 2026. Defendants may respond to the complaint, including by moving to dismiss under the heightened pleading standards of the Private Securities Litigation Reform Act.

SEC Filings & Risk Factors

The complaint targets a series of SEC filings spanning the class period, each of which contained detailed preclinical comparisons between ERAS-0015 and Revolution Medicines' RMC-6236. The central allegation is that these filings presented a misleadingly favorable competitive picture while concealing material intellectual property risks and the inherent limitations of the underlying data.

The 2024 10-K, filed on March 20, 2025, contained the most extensive comparative data. It disclosed multiple preclinical metrics, including ERAS-0015's "8-21-fold higher binding affinity to cyclophilin A relative to RMC-6236," "an average of 5 times greater potency" in vitro, "comparable to greater in vivo antitumor activity at doses which were approximately one-tenth to one-eighth of the dose of RMC-6236," and superiority on "three key metrics" in a head-to-head pharmacokinetic comparison. The filing also stated that the company's IP was robust and that the drug's "potential to address unmet medical needs in approximately 2.7 million patients" made ERAS-0015 the centerpiece of a "reprioritization program" that would "deemphasize" other drug initiatives. What the filing did not disclose, according to the complaint, was that these comparisons placed Erasca at risk of patent and trade secret challenges from Revolution Medicines, or that the data underlying the comparisons was based on cross-study analyses that were not directly comparable.

The January 12, 2026 Form 8-K presentation reiterated and expanded upon these same comparisons, featuring slide after slide with titles explicitly benchmarking ERAS-0015 against RMC-6236. The 2025 10-K, filed on March 12, 2026, repeated the preclinical comparison data from the 2024 filing and added clinical safety data stating that ERAS-0015 had shown "favorable safety and tolerability results, with no dose-limiting toxicities and predominantly low-grade adverse events observed at all dose levels evaluated." According to the complaint, neither filing disclosed the alleged patent and trade secret risks or the limitations of the cross-study comparison methodology.

The corrective filings on April 27, 2026 revealed a dramatically different picture. The first 8-K disclosed that Revolution Medicines had alleged patent infringement under U.S. Patent No. 12,409,225 and trade secret misappropriation, and had demanded that Erasca stop making "deceptive and untrue comparative statements comparing ERAS-0015 and RMC-6236."

The second 8-K, filed that evening, disclosed a patient death in the Phase 1 trial and included language acknowledging that the comparisons were based on cross-study analyses, were "not based on any head-to-head clinical trials," and were "inherently limited and such data may not be directly comparable." According to the complaint, that qualification was absent from the challenged prior statements.

The overall pattern, as characterized in the complaint, is one of sustained and detailed competitive benchmarking that formed the core of Erasca's investment thesis, presented without disclosing either the intellectual property vulnerabilities those comparisons created or the fundamental methodological limitations of the underlying data. The complaint alleges that these omissions were material to investors because the comparative narrative was central to Erasca's investor communications and the January 2026 offering.

How to Check Whether You May Be Eligible in the Erasca, Inc. (ERAS) Class Action

• Confirm you purchased ERAS shares during the January 14, 2025 to April 26, 2026 class period
• Review the allegations and eligibility requirements in the pending securities class action
• Gather trade confirmations and brokerage records documenting purchases or losses
• Consult counsel regarding lead plaintiff deadline, eligibility, and any potential rights or options

Disclaimer: Attorney Advertising. This shareholder alert is for informational purposes only and does not constitute legal advice. Consult a qualified attorney for personalized guidance. No specific outcomes are guaranteed.