Exelixis is giving up on its tissue factor (TF)-targeting antibody-drug conjugate after concluding the candidate was unlikely to best Pfizer and Genmab’s Tivdak.
The biotech had been evaluating the ADC, dubbed XB002, in the phase 1 JEWEL-101 trial in advanced solid tumors and said that it would unveil the data “at a later date.” But, based on what the company has seen so far, Exelixis said the compound “is unlikely to improve upon” tisotumab vedotin—an approved TF-focused ADC marketed for cervical cancer as Tivdak—“or other competitor TF-targeting ADCs currently in development.”
Resources from the XB002 program will be reallocated to the late-stage tyrosine kinase inhibitor zanzalintinib, as well as the phase 1 USP1 inhibitor XL309 and the biotech’s “growing pipeline,” Exelixis said in its second-quarter earnings release.
Exelixis isn’t ready to give up on ADCs quite yet. The company pointed out that XB371, its ADC consisting of a topoisomerase payload conjugated to a TF-targeting monoclonal antibody, remains in preclinical development.
In his statement to accompany the release, Exelixis CEO Michael Morrissey, Ph.D., focused the spotlight on Cabometyx, which is already approved for renal cell carcinoma, hepatocellular carcinoma and thyroid cancer. The Ipsen-partnered tyrosine kinase inhibitor brought in $433.3 million in net U.S. revenues in the second quarter and the FDA is mulling an application to approve the drug in advanced neuroendocrine tumors (NETs).
“We’re actively preparing for launch and excited at the prospect of bringing this new treatment option to previously treated advanced NET patients with high unmet medical need,” Morrissey said.
“At the same time, we are prioritizing our clinical pipeline with plans to initiate a new phase 3 pivotal trial for zanzalintinib in NET, advance phase 1 efforts for XL309 and XB010, and discontinue development of XB002,” the CEO added.
“In our view, Exelixis enters 2024 at an inflection point, in which the growth of its flagship Cabometyx franchise is stabilizing while pipeline programs, especially zanzalintinib, are holding increasing responsibility to offset Cabometyx’s market exclusivity expiry in 2031,” William Blair analysts said in an Aug. 7 note.
“In the midterm, NETs and [metastatic castration-resistant prostate cancer] could emerge as material growth opportunities for the franchise,” the analysts added.
It’s been a year of change at Exelixis, which laid off 175 employees—equivalent to around 13% of its workforce—in January as part of a broader restructuring aimed at “concentrate[ing] R&D resources to advance our emerging pipeline.”
At the time, that strategy included progressing XB002 through a phase 1 trial. Exelixis had licensed the ADC from Iconic Therapeutics back in 2020, citing preclinical data that supported the asset’s “best-in-class potential in treatment of solid tumors.”