Background of the Complete Partnership Termination

Eli Lilly (LLY) has terminated its co-development and technology transfer agreement with Rigel Pharmaceuticals (RIGL) for ocadusertib (R552), a Receptor-interacting serine/threonine-protein kinase 1 (RIPK1) inhibitor. Following the termination of development for Central Nervous System (CNS) disease indications in November 2025, the company has now completely dissolved the remaining collaborative relationship for non-CNS indications, including Rheumatoid Arthritis (RA). Lilly stated that the decision to discontinue development was made because ocadusertib did not meet the company's high criteria for late-stage clinical entry. As a result, the large-scale deal, valued at $960 million, concluded in 2021, has been officially terminated.

Limitations of the Rheumatoid Arthritis Market and Strategic Repositioning

This decision can be analyzed as a move by Lilly to reallocate resources in the global Rheumatoid Arthritis (RA) market, which is worth approximately $30 billion annually. Existing treatments such as adalimumab and other TNF inhibitors, biologics, and JAK inhibitors already dominate the market, and new drugs with novel mechanisms of action must demonstrate overwhelming efficacy to be commercialized. Ocadusertib is currently in Phase 2 clinical trials, and its commercialization would require significant costs. However, it appears that it did not meet Lilly's high efficacy standards. Ultimately, Lilly determined that focusing research and development (R&D) resources on other high-growth pipelines, such as obesity or other immune diseases, would be more beneficial in terms of opportunity cost.

The Difficult History of RIPK1 Inhibitors and the Crisis of the Entire Class

This partnership termination is not just a problem for Rigel, but an extension of the long-term underperformance of the entire RIPK1 target class. In March 2026, Roche's subsidiary Genentech discontinued Phase 2 clinical trials of flizasertib, a RIPK1 inhibitor for Acute Kidney Injury (AKI), and completely removed it from its pipeline due to lack of efficacy. Sanofi, together with Denali Therapeutics (DNLI), also discontinued the development of oditrasertib, which had previously failed in clinical trials for Amyotrophic Lateral Sclerosis (ALS) and Multiple Sclerosis (MS), and reduced the priority of its autoimmune disease candidate, eclitasertib, effectively ending the collaboration. As global pharmaceutical companies have repeatedly failed to secure the efficacy and safety of RIPK1 inhibitors, confidence in this mechanism in the capital market has plummeted beyond the clinical threshold.

Rigel's Financial Pressure and the Difficult Path of Independence

With the dissolution of the alliance with Lilly, Rigel Pharmaceuticals (RIGL), a mid-sized biotechnology company, faces significant financial setbacks and is now facing the challenge of independent survival. As a result of the contract termination, all global rights related to ocadusertib are returned to Rigel, but Rigel will no longer be able to receive the remaining milestone payments and commercial royalties, totaling up to $835 million, that it had expected from Lilly. Rigel's financial resources are limited, making it difficult to independently complete the ongoing Phase 2 clinical trial for Rheumatoid Arthritis (NCT05848258). It needs to find a new global partner, but the history of Lilly's termination will act as a negative signal, making it extremely difficult to secure a new deal. As a result, Rigel is destined to rely on sales of existing commercial products and embark on a period of austerity, drastically reducing research and development costs.