Rigel’s Veppanu scores its first nod in HER2-, ER+, ESR1-mutant locally-advanced or metastatic breast cancer, making it the first PROTAC approved
Veppanu (Rigel Pharmaceuticals) was approved by the FDA on May 1, 2026 and targets ESR1-mutations, which often arise following treatment with aromatase inhibitors, a staple in the 1L breast cancer paradigm. Its approval is based on the Phase III VERITAC-2 trial, run by Pfizer and its co-developer Arvinas, who licensed Veppanu to Rigel Pharmaceuticals in a $405 million milestone-based deal that officially closed on June 11, 2026. [1, 2]
Protein degraders are among the most exciting drug classes, with dozens of ongoing clinical development programs in a slew of indications from prostate and breast cancers all the way to Alzheimer’s and Parkinson’s Disease. Rather than merely blocking the active site or downstream signaling of an oncogenic protein like traditional small molecule inhibitors (SMIs), protein degraders cause their destruction. These drugs are effective at overcoming resistance mutations, but offer inferior pharmacokinetics when compared to SMIs.
The first monovalent protein degrader to be introduced in breast cancer was Faslodex (AstraZeneca), which was later followed by other selective estrogen receptor degraders (SERDs). While effective, these drugs bind to the estrogen receptor and are stoichiometric in nature, meaning each drug molecule indirectly leads to the destruction of exactly one estrogen receptor. PROTACS, or “bivalent protein degraders,” on the other hand, are catalytic in nature with each molecule directly causing the destruction of multiple estrogen receptors. This fast-acting and potent approach is expected to transform a variety of landscapes in the coming years.
Despite its mechanistic novelty, Veppanu has its work cut out for it as the PROTAC’s approval comes three years behind that of next-gen SERD Orserdu (Stemline Therapeutics) and one year behind Inluriyo (Eli Lilly and Company). Each next-gen agent displayed strong Clinical Innovation over the first-generation SERD, Faslodex in their respective trials (Figure 1A,B).
Veppanu likewise showcased a dominant performance over Faslodex, with a 0.57 hazard ratio for progression-free survival (p-value = 0.0001), establishing itself as a viable option in the space (Figure 1C). [3]
Figure 1: Drivers of Clinical Innovation for Each Protein Degrader, Each Compared with Its Respective Control Arm
However, when compared head-to-head with Inluriyo, there is little differentiation to speak of aside from slight efficacy gains, which are moderately clawed back due to cost. The result is a Clinical Innovation score of 1.6%, well below the traditional differentiation benchmark of 5%. Unless Veppanu is able to post a better-than-expected median overall survival when the endpoint matures, it will likely only split the branded market with Inluriyo and Orserdu (Figure 2).
Figure 2: Drivers of Clinical Innovation, Veppanu vs. Inluriyo
Notwithstanding, this approval not only marks the beginning of an exciting development in pharmaceuticals, but also brings another treatment option to a historically underserved population.
[1] Pfizer. A Phase 3, Randomized, Open-Label, Multicenter Trial of ARV-471 (PF-07850327) vs Fulvestrant in Participants With Estrogen Receptor-Positive, HER2-Negative Advanced Breast Cancer Whose Disease Progressed After Prior Endocrine Based Treatment for Advanced Disease (VERITAC-2). ClinicalTrials.gov identifier: NCT05654623. Updated March 18, 2026. Accessed August 18, 2026. https://clinicaltrials.gov/study/NCT05654623
[2] Rigel enters exclusive global licensing agreement for VEPPANU (vepdegestrant), an oral PROTAC, for the treatment of 2L+ ER+/HER2-, ESR1m advanced or metastatic breast cancer. News release. Rigel Pharmaceuticals, Inc.; May 12, 2026. Accessed August 18, 2026. https://www.rigel.com/news-media/press-releases/detail/437/rigel-enters-exclusive-global-licensing-agreement-for
[3] FDA approves vepdegestrant for ER-positive, HER2-negative, ESR1-mutated advanced or metastatic breast cancer. US Food and Drug Administration. May 1, 2026. Accessed August 18, 2026. https://www.fda.gov/drugs/resources-information-approved-drugs/fda-approves-vepdegestrant-er-positive-her2-negative-esr1-mutated-advanced-or-metastatic-breast