Anaptys' Legal Motion: A Tactical Delay in the Path to Separation

The immediate event is a procedural filing. On December 30, 2025, AnaptysBio filed a partial motion to dismiss Tesaro's claim of anticipatory breach in Delaware Chancery Court. The motion was unsealed just last week, on January 8, 2026. This is not a new lawsuit, but a tactical response to one filed by Tesaro, a subsidiary of GSK, in November.

The mechanics are specific. Anaptys is leveraging Delaware's anti-SLAPP (Strategic Lawsuit Against Public Participation) law. The company argues that Tesaro's lawsuit is a strategic attempt to gain leverage ahead of Anaptys' planned 2026 separation. In essence, Anaptys contends that its own efforts to resolve the underlying royalty dispute through good-faith talks should not be construed as a repudiation of the contract. The motion explains why, as a matter of law, Anaptys has never repudiated the agreement and why the anti-SLAPP statute applies to prevent such strategic litigation.

The direct impact is a clear delay. The court is expected to hear Anaptys' Motion to Dismiss by early March 2026. This will push the full trial date for all claims to July 14-17, 2026. For a company racing to separate its royalty business by year-end, this is a significant procedural win. It buys time and forces the legal threat to wait.

The thesis is clear: this is a tactical delay, not a resolution. The underlying royalty dispute remains the key overhang for the separation. The motion only challenges one claim; it does not address the core allegations of breach or the future of the royalty stream. The legal battle is simply being re-routed down a longer procedural path.

The Stakes: Royalties and the Separation Thesis

The financial value at stake is immense. The royalty agreement with GSK covers Jemperli, a drug showing strong commercial traction, with sales growing to $785 million year-to-date in 2025. More importantly, the royalty term extends at least through the expiration of composition-of-matter coverage on the drug's molecule, which is set for 2035 in the U.S. That's a multi-decade revenue stream, with Anaptys anticipating annualized Jemperli royalties of more than $390 million at GSK's peak sales guidance of over $2.7 billion.

This royalty stream is the core of Anaptys' strategic plan. The company has explicitly announced its intent to separate its biopharma operations from its substantial royalty assets by year-end 2026. The goal is to unlock value by creating two distinct public companies: one focused on developing its pipeline of immunology drugs, and another dedicated to managing and protecting the cash flow from collaborations like the Jemperli royalty. As CEO Daniel Faga stated, this separation is designed to provide investors with the opportunity to realize and enhance the potential value of two distinct sets of assets.

The July 2026 trial date is the critical inflection point. A negative outcome for Anaptys could severely devalue this entire royalty asset. The company's own motion argues it has never repudiated the agreement, but the lawsuit alleges otherwise. If Tesaro's claim of anticipatory breach is upheld, it could cast doubt on the validity of the royalty payments themselves, directly threatening the financial foundation of the planned separation.

The royalty tiers are structured to reward scale, which amplifies the stakes. The agreement calls for 8% of net sales below $1.0 billion, 12% between $1.0B and $1.5B, 20% between $1.5B and $2.5B, and 25% above $2.5B. With GSK guiding to peak sales far above $2.7 billion, the top tier is highly relevant. Any legal uncertainty around the royalty's future could depress the perceived value of that high-margin portion, making the separation far less attractive to investors. For now, the motion to dismiss buys time, but the separation thesis hinges entirely on the outcome of the trial scheduled for next summer.

Near-Term Catalysts and Tactical Setup

The immediate financial and clinical events will determine if the legal overhang is already priced in or if the separation creates a mispricing. The primary near-term catalyst is a massive revenue inflection. Anaptys expects to accrue a one-time $75 million commercial sales milestone in Q4 2025 once Jemperli hits $1 billion in worldwide net sales. This is a direct, cash-positive event that should occur imminently, given the drug's sales of 600 million pounds, or about $785 million, through the first nine months of 2025. This milestone, combined with the already-secured > $390 million in annualized Jemperli royalties payable to Anaptys at GSK's peak sales guidance of > $2.7 billion, provides a powerful near-term cash flow anchor that could support the stock through the legal delay.

Clinically, the setup is also building momentum. Key data readouts are scheduled for late 2025 and early 2026. The most notable is the late-breaking oral presentation of Phase 2b data for rosnilimab in rheumatoid arthritis at ACR Convergence 2025, which has already been delivered. The company also anticipates top-line Phase 2 data through Week 12 for rosnilimab in ulcerative colitis in November or December. These clinical catalysts are critical for the biopharma leg of the separation thesis, demonstrating value in the pipeline assets that will form the new company.

Viewed together, these events create a tactical opportunity. The market may be overreacting to the motion's filing, focusing on the delayed threat while overlooking the immediate cash flow and clinical progress. The analyst note suggesting GSK/Tesaro may be trying to use leverage ahead of the 2026 separation underscores this dynamic. The filing is a procedural win, but the separation timeline remains intact. If the stock dips on legal news while the $75 million milestone and clinical data are on the horizon, it could create a temporary mispricing. The gap between the delayed trial date and the separation deadline offers a window where the underlying value of the royalty stream and pipeline may not be fully reflected in the share price.