Vepdegestrant (ARV-471): The First PROTAC to Reach the Market
On May 1, 2026, the FDA approved vepdegestrant (ARV-471, marketed as Veppanu) for adults with estrogen receptor (ER)-positive, HER2-negative, ESR1-mutated advanced or metastatic breast cancer whose disease has progressed after at least one line of endocrine therapy, together with a companion diagnostic that calls ESR1 mutations from circulating tumor DNA.1 The agency cleared the application a month ahead of its goal date.
It is the first proteolysis-targeting chimera (PROTAC) ever approved.2 The modality was introduced in 2001 as a peptide-based proof of concept,3 and twenty-five years later it has a marketed small-molecule drug. For synthetic chemists, the more interesting fact is what that drug looks like: a 724 Da heterobifunctional molecule carrying three defined stereocenters and a calculated logP of 6.8, sitting comfortably outside rule-of-five space.4
ER-Positive Breast Cancer Treatment Resistance: ESR1 Mutations and Endocrine Therapy Failure
Roughly 70% of newly diagnosed breast cancers are ER-positive, and their growth is driven by estrogen signalling through ERα.4 Standard endocrine-based treatment works well but can eventually fail in several ways, including:
Activating ESR1 mutations, which allow ligand-independent coactivator binding and reduce sensitivity to aromatase inhibitors, SERMs, and SERDs alike.5
Delivery problems with fulvestrant, the reference SERD, which has poor solubility and no useful oral bioavailability. This forces 500 mg intramuscular dosing, and it eliminates only part of the receptor pool.
Resistance to CDK4/6 inhibitors, which does not remove ER dependence. Many tumours that progress on a CDK4/6 inhibitor continue to run on ER-driven transcription, so the upstream driver is still there to be removed.4
PROTACs give drug hunters a way around the “occupancy problem”, where a drug’s effect depends on keeping the binding site filled. Rather than binding the receptor and holding it, a PROTAC recruits an E3 ligase, triggers ubiquitination and proteasomal destruction of the target, then dissociates and does it again. The pharmacology is event-driven and catalytic instead of stoichiometric, and it does not care what conformation the receptor has adopted, which is precisely why ESR1 mutants remain vulnerable.
Structure Features of Vepdegestrant (ARV-471)
Vepdegestrant consists of three principal structural elements:
Estrogen receptor-binding fragment: A cis-1,2-diaryltetralin scaffold related to lasofoxifene, incorporating a hydroxytetrahydronaphthalene core.
Cereblon-recruiting fragment: A glutarimide–isoindolinone motif related to lenalidomide.
Linker: A connecting unit containing piperazine that joins the two binding fragments.
The combination of these fragments creates a route-planning problem that extends beyond the synthesis of either fragment independently. A practical retrosynthetic analysis must account for stereochemical requirements, the functional groups needed for fragment coupling, and the compatibility of the proposed transformations with the overall molecular structure.
Figure 1 The chemical structure of vepdegestrant (ARV-471) with highlighted fragments derived from lasofoxifene (red) and lenalidomide (blue)
Retrosynthesis Analysis of Vepdegestrant Using ChemAIRS®
Retrosynthetic analysis of vepdegestrant with the ChemAIRS® Process Chemistry module produced multiple route proposals. One representative strategy comprises 16 known synthetic steps, with a longest linear sequence (LLS) of seven steps. The proposed route draws on established transformations and commercially available starting materials.
Scheme 1 Retrosynthetic analysis of vepdegestrant using ChemAIRS®, showing a convergent route assembled from established synthetic chemistry
The route divides the target into two principal branches: the cereblon-recruiting fragment and the cis-tetralin fragment. Preparing these fragments separately allows their individual synthetic sequences to be evaluated before the final stages of assembly.
Synthesis of the Cereblon-Recruiting Fragment 16b
The lower branch of the proposed route follows a sequence closely related to published approaches used to prepare the cereblon-containing intermediate 16b on manufacturing scale. Starting from methyl benzoate derivative 3a, the proposed sequence reaches aldehyde 6a through three steps. This sequence corresponds to chemistry reported during the early clinical development of vepdegestrant, although ChemAIRS® retrieved reaction conditions from alternative sources.
Subsequent transformations connect the relevant intermediates through reductive amination and glutarimide formation, accompanied by removal of the Boc protecting group from piperazine, to furnish intermediate 16b.
The agreement with published chemistry provides a useful reference point for evaluating the proposed route. It also illustrates how established transformations can be combined into a coherent synthetic sequence using information from multiple sources.
Scheme 2 ChemAIRS®-inspired synthesis of the cereblon-recruiting fragment (16b) of vepdegestrant (ARV-471)
Synthesis of the Cis-Tetralin Fragment 14b
The upper branch of the route leads to aldehyde 16a and follows a strategy broadly consistent with the reported manufacturing approach.
One notable difference concerns the order of stereochemical installation and fragment attachment. In the ChemAIRS® proposal, the stereochemistry of the cis-tetralin intermediate 14b is established before the attachment of piperidine fragment 14a. This reverses the order used in the reported route while retaining a strategy based on established chemistry.
Scheme 3 ChemAIRS®-inspired synthesis of the cis-tetralin fragment (16a) of vepdegestrant (ARV-471)
This alternative sequence highlights an important consideration in route design: the same target structure can sometimes be approached through different orders of bond formation and stereochemical control. Evaluating these alternatives requires attention to intermediate accessibility, selectivity, and compatibility across the full sequence.
Vepdegestrant Synthesis: ChemAIRS® Route vs. Published Process
The proposed ChemAIRS® route shows substantial agreement with published vepdegestrant synthesis, particularly in the preparation of the cereblon-recruiting fragment. It also differs in the sequence used to establish stereochemistry and attach the piperidine fragment. The proposed route comprises 16 steps, with a longest linear sequence (LLS) of seven steps. These differences provide a basis for comparing retrosynthetic strategies, while experimental performance and scalability require independent evaluation.
Vepdegestrant (ARV-471): Retrosynthetic Route Analysis with ChemAIRS®
The ChemAIRS® Process Chemistry analysis produced a convergent, 16-step route to vepdegestrant, with a longest linear sequence (LLS) of seven steps. The cis-tetralin fragment 16a and cereblon-recruiting fragment 16b are prepared along separate branches using established transformations and commercially available starting materials before converging in the later stages of the synthesis.
Despite limited reliance on the reported manufacturing route, the proposed sequence reproduces much of its overall strategy. One notable difference is the order of stereochemical installation and piperidine attachment: ChemAIRS® establishes the cis-tetralin stereochemistry at 14b before attaching piperidine 14a, reversing the sequence reported in the manufacturing approach.
This analysis illustrates how retrosynthetic route planning can identify established chemistry that aligns with a published process while also suggesting alternative synthetic sequences. For process chemists, such proposals provide a starting point for evaluating route options, with experimental validation needed to establish reaction performance, selectivity, and scalability.
References
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 5, 2026. https://www.fda.gov/drugs/resources-information-approved-drugs/fda-approves-vepdegestrant-er-positive-her2-negative-esr1-mutated-advanced-or-metastatic-breast
Arvinas announces FDA approval of VEPPANU (vepdegestrant) for the treatment of ESR1m, ER+/HER2- advanced breast cancer. Arvinas, Inc. May 1, 2026. Accessed August 5, 2026. https://ir.arvinas.com/news-releases/news-release-details/arvinas-announces-fda-approval-veppanu-vepdegestrant-treatment/
Ma Z, Zhou J. NDA submission of vepdegestrant (ARV-471) to U.S. FDA: the beginning of a new era of PROTAC degraders. J Med Chem. 2025;68(14):14129-14136. https://doi.org/10.1021/acs.jmedchem.5c01818
Tang C, Tian B, Zhang B, et al. Insights into vepdegestrant (ARV-471): the first-in-class estrogen receptor proteolysis-targeting chimera approaching Food and Drug Administration approval for breast cancer. ChemMedChem. 2026;21:e202501111. https://doi.org/10.1002/cmdc.202501111
Rej RK, Thomas JE II, Acharyya RK, Rae JM, Wang S. Targeting the estrogen receptor for the treatment of breast cancer: recent advances and challenges. J Med Chem. 2023;66(13):8339-8381. https://doi.org/10.1021/acs.jmedchem.3c00136
a) Chen CH, Dong H, inventors; Arvinas Operations, Inc., applicant. Methods of Manufacturing a Bifunctional Compound. WIPO patent WO2023/009521A1. February 2, 2023. b) Bernhardson DJ, Fifer J, Girvin ZC, et al. A Second-Generation Route to the Cereblon Fragment of ARV-471, Vepdegestrant. Org. Process Res. Dev. 2025;29:2636-2648. https://doi.org/10.1021/acs.oprd.5c00271
Avery S, Buske JM, Chen D, et al. Development of a Commercial Manufacturing Process for Vepdegestrant, an Orally Bioavailable PROTAC Estrogen Receptor Degrader for the Treatment of Breast Cancer. Org. Process Res. Dev. 2024;28;4079. https://doi.org/10.1021/acs.oprd.4c00362