Veppanu’s FDA Success and the Future of Targeted Protein Degradation
At the beginning of the month, a milestone decades in the making was reached. Veppanu (vepdegestrant, ARV-471) was approved by the US Food and Drug Administration for the treatment of adults with oestrogen receptor-positive (ER+), HER2-negative, ESR1-mutated advanced or metastatic breast cancer. Developed by Arvinas and Pfizer, Veppanu is the first-ever FDA-approved PROteolysis TArgeting Chimera, better known as a PROTAC.
For the chemistry and drug discovery community, this approval is the culmination of a scientific journey that began with a concept paper in 2001 and has steadily built to this regulatory breakthrough. For patients with a particularly hard-to-treat breast cancer subtype, it offers new treatment options. For researchers working in targeted protein degradation, it marks an important proof of concept for the entire modality.
PROTAC Recap: What Do They Do?
Unlike small molecule inhibitors or antagonists, which block a target protein’s activity, but leave it intact, PROTACs are bifunctional degrader molecules that recruit the cellular ubiquitin-proteasome system to eliminate the protein entirely. The degrader itself is catalytic and can act at lower concentrations than classical inhibitors. Moreover, they don’t necessarily need to bind to an active site, so proteins once considered undruggable are now accessible routes for treatment.
In the specific case of vepdegestrant, this logic is applied to the oestrogen receptor (ER), bringing it and an E3 ubiquitin ligase together to form a ternary complex, triggering the receptor’s degradation. Now it is approved as an oral, once-daily alternative to the injectable fulvestrant, which was until now the standard of care for these breast cancers.
The Clinical Case: ESR1 Mutations and Endocrine Resistance
ER-positive/HER2-negative breast cancer accounts for the majority of all breast cancer cases, and first-line treatment with CDK4/6 inhibitors plus endocrine therapy has transformed outcomes over the past decade. The challenge comes at relapse. When disease progresses after CDK4/6 inhibitor-based therapy, acquired ESR1 mutations that render the ER constitutively active and resistant to standard endocrine agents are detected in around 40% of patients. Fulvestrant, a selective oestrogen receptor degrader (SERD) was developed to sidestep this issue, inducing misfolding in the ER, ultimately leading to its degradation. Veppanu offers a similar, but different, approach, inducing degradation through an alternative mechanism.
The VERITAC-2 Data
FDA approval was based on VERITAC-2 (NCT05654623), a global, randomised, open-label Phase 3 trial of 624 patients across 26 countries. All had progressed on at least one prior line of endocrine therapy including a CDK4/6 inhibitor; patients were randomised to oral vepdegestrant (200 mg once daily) or intramuscular fulvestrant.
In the ESR1-mutant population (n=270), results were clear-cut: median progression-free survival was 5.0 months with vepdegestrant versus 2.1 months with fulvestrant (HR 0.57; p=0.0001) — a 43% reduction in risk of progression or death. Objective response rate was 19% versus 4%. Separately reported patient-reported outcome data from VERITAC-2 also showed vepdegestrant treatment significantly delayed deterioration in quality of life, pain, and functioning.
A Detailed Understanding of Veppanu
The VERITAC-2 results invite a more nuanced reading. The trial did not reach statistical significance in the overall intent-to-treat population: the benefit was specific to patients with confirmed ESR1 mutations, not all comers with ER+/HER2- disease. This reflects an important biological reality: vepdegestrant’s clinical advantage over fulvestrant is most pronounced precisely where acquired resistance to standard endocrine agents is highest.
Overall survival (OS) data also remain immature – only 16% of the required events had occurred at the time of the progression-free survival (PFS) analysis – so the longer-term picture is still developing. And the five-month median PFS, while statistically superior and clinically meaningful for a refractory population, is a promise, rather than proof of improved OS rates. These limitations point naturally toward combination strategies, where the early data are considerably more encouraging.
Room to Grow: Combinations and the Broader PROTAC Pipeline
Phase 1b results pairing vepdegestrant with palbociclib (Ibrance) demonstrated a median PFS of 11.2 months in the overall population and 13.7 months in the ESR1-mutant subgroup – more than double the monotherapy result, with objective response rates of 42–47%. Combining ER degradation with CDK4/6 inhibition appears to address some of the resistance mechanisms that limit monotherapy benefit and combination trials are ongoing.
Beyond vepdegestrant, the broader PROTAC pipeline is moving quickly. By mid-2025, two further candidates had reached Phase 3:
- Catadegbrutinib (BGB-16673): a BTK degrader showing ORRs of ~85% in relapsed/refractory CLL/SLL in Phase 1/2 data from the CaDAnCe-101 trial
- Gridegalutamide (BMS-986365): an androgen receptor degrader in Phase 3 for metastatic castration-resistant prostate cancer
Earlier-stage programmes are expanding the target landscape considerably: BCL6, KRAS, MYC, tau, and alpha-synuclein are all under investigation, with some PROTAC candidates moving into neurodegeneration as well as oncology. Next-generation designs – dual-targeting PROTACs, photocaged variants that activate only in target tissue, phosphorylation-dependent molecules – are tackling the persistent challenges of oral bioavailability and tissue selectivity that remain active areas of research.
The Bigger Picture
Veppanu’s approval is the end of the beginning for PROTAC therapeutics. The seven-year span from first PROTAC clinical trial (2019) to first approved drug (2026) is, by the standards of drug development, remarkably fast. We’re now seeing the ultimate validation of the chemistry, biology and clinical strategy that have underpinned this modality since Craig Crews and colleagues first proposed the concept.
While the remaining questions around vepdegestrant itself are relatively contained, their answers will help complete the picture on what this first approved PROTAC can ultimately deliver. The broader challenges of the modality, from improving oral bioavailability and tissue selectivity to expanding into genuinely undruggable target classes, remain very much open. That work is well underway.
