Hengrui's ADC Enters First-Line Breast Cancer: PFS Met, but How Far From Reshaping the Landscape?

Hengrui Pharma's ADC Enters First-Line Breast Cancer: PFS Endpoint Met, but How Far From Reshaping the Landscape?

The drug secures a critical foothold in the race for the HER2-positive first-line market.

On August 31, Jiangsu Hengrui Pharmaceuticals Co., Ltd. (600276.SH / 01276.HK) announced that its HER2-targeted antibody-drug conjugate (ADC), Recombinant Trastuzumab (SHR-A1811), developed by subsidiary Suzhou Shengdia, met its primary endpoint of progression-free survival (PFS) in an interim analysis of the pivotal Phase III SHR-A1811-307 trial for first-line treatment of HER2-positive recurrent or metastatic breast cancer.

Moving from later-line therapy to the first-line setting represents a critical step in unlocking the full value of this domestically developed ADC. However, overall survival (OS) data remain immature, questions persist about how to weigh the two trial arms, and long-term safety outcomes still require full validation.

A Clinical Milestone With Dual Significance

Results showed that compared with the standard THP regimen — docetaxel combined with trastuzumab and pertuzumab — SHR-A1811, whether used with or without pertuzumab, significantly prolonged PFS with both statistical and clinical significance.

The trial, led by Prof. Jiang Zefei and Prof. Yin Yongmei, enrolled 868 patients across 75 clinical centers nationwide. The company plans to submit a pre-NDA consultation application to China's Center for Drug Evaluation (CDE) to advance registration for the first-line indication.

For more than a decade, THP has been the dominant first-line standard for HER2-positive advanced breast cancer. The regimen relies on chemotherapy combined with dual targeted therapy for disease control, but chemotherapy-induced bone marrow suppression and gastrointestinal side effects can persistently affect patients' quality of life.

The Phase III study employed a dual-arm design, simultaneously evaluating SHR-A1811 plus pertuzumab and SHR-A1811 monotherapy. The pertuzumab-free arm is particularly noteworthy: if supported by complete data, this regimen could reduce combination therapy burden and offer clinicians a new treatment option.

Notably, the company has only disclosed interim PFS results. OS data remain immature, and complete safety profiles have yet to be revealed. The indication still faces a full regulatory review process before formal submission and approval.

From Later-Line to First-Line: A Commercial Step Up

SHR-A1811 is a next-generation HER2-targeted ADC independently developed by Hengrui Pharma, with a drug-to-antibody ratio (DAR) of 6. It works by binding to HER2-expressing tumor cells, triggering internalization, and releasing cytotoxic payloads through protease cleavage within lysosomes, inducing cell-cycle arrest and tumor-cell apoptosis.

Previously, clinical validation of SHR-A1811 focused primarily on later-line treatment — addressing unmet needs after standard regimens fail. A first-line approval, however, would place the drug in the preferred treatment sequence for treatment-naive patients, significantly expanding its addressable market.

Looking at the trajectory of trastuzumab deruxtecan (T-DXd, formerly DS-8201), which transformed the global HER2-positive breast cancer treatment paradigm, a first-line breakthrough represents a pivotal inflection point for domestic ADCs seeking to elevate both clinical and commercial value.

Within China's HER2 ADC landscape, multiple products have already gained regulatory approval, with imported therapies and domestic innovators now competing head-to-head. In breast cancer, the competitive focus has shifted from later-line settings to the first-line frontier. Globally, ADCs continue to reshape HER2-positive tumor treatment paradigms, with reducing chemotherapy and combination therapy emerging as key clinical exploration directions.

SHR-A1811's dual-arm design directly benchmarks against the established THP gold standard, seeking to answer the core clinical question: Can an ADC replace conventional chemotherapy plus dual targeted therapy? If the data prove robust, the results could provide clinicians with a new option balancing efficacy and safety, and potentially propel domestic ADCs from follow-on innovation to a role in defining first-line treatment standards.

At the corporate level, SHR-A1811 is one of the core assets in Hengrui Pharma's innovative pipeline, spanning multiple major tumor types including lung cancer, breast cancer, and colorectal cancer, with several Phase III trials underway. A successful first-line breast cancer approval would meaningfully expand the product's commercial potential and could become a significant growth driver for the company's innovative drug portfolio.

PFS Is Just an Entry Ticket — Multiple Tests Remain

A positive interim PFS result in the Phase III trial marks a critical step forward for SHR-A1811's first-line ambitions, but realizing its full clinical and commercial value will require clearing several remaining hurdles.

First, overall survival. OS is a crucial measure of long-term benefit in advanced oncology drugs. With OS data still immature, whether the PFS advantage translates into a survival benefit requires continued follow-up. Determining which of the two trial arms offers the superior benefit-risk profile will depend on the complete dataset.

Second, safety. ADCs require particular attention to special adverse events such as interstitial lung disease. SHR-A1811's long-term safety profile in a large, first-line population remains to be observed. Reducing combination therapy does not necessarily mean lower toxicity — the final verdict will depend on adverse-event rates, discontinuation rates, and quality-of-life data.

Third, commercialization. Even with a successful approval, the product will face intense competition. Imported ADCs already hold a first-mover advantage. Factors including medical insurance coverage, hospital formulary access, physician education, and patient affordability will all influence real-world penetration. Meanwhile, other domestic ADCs targeting the same pathway continue to advance through clinical development, potentially intensifying competition further.

From an industry perspective, the ADC track is characterized by high R&D costs and substantial clinical risk. The journey from a positive Phase III interim analysis to NDA submission and final approval still carries meaningful uncertainty. Even after approval, achieving a comprehensive advantage in efficacy, safety, pricing, and clinical accessibility will determine the product's ultimate market position.

The Bottom Line

The positive interim PFS result from the SHR-A1811-307 trial represents a significant milestone in domestic HER2 ADC development, demonstrating that locally developed innovative drugs can credently challenge internationally accepted first-line standards.

But a positive PFS is merely an entry ticket to the first-line market — not the endgame. Subsequent OS data, complete safety results, the benefit-risk comparison between the two regimens, regulatory progress, and commercial performance will be the true measures of SHR-A1811's real value. Whether it can genuinely reshape the first-line treatment landscape for HER2-positive breast cancer will depend on the complete data yet to come.