The quiet revolution in cancer treatment is no longer so quiet.
For years, the world of oncology largely operated on a binary understanding of HER2 status: either a tumor was HER2-positive, opening the door to targeted therapies, or it was HER2-negative, relegating patients to more conventional, often less precise, treatments.
But a seismic shift is underway, driven by groundbreaking scientific understanding and the advent of sophisticated new drugs.
This shift recognizes a critical, often overlooked, middle ground: HER2-low cancers.
And the market for treating these previously underserved patient populations is poised for explosive growth, projected to swell from USD 3.2 billion in 2024 to a staggering figure by 2034, registering a robust compound annual growth rate (CAGR) of 9.4%.
This burgeoning market, as highlighted by DelveInsight’s recent report, is fundamentally reshaping the treatment landscape.
At its heart lies the remarkable success of Antibody-Drug Conjugates (ADCs), particularly ENHERTU (trastuzumab deruxtecan).
This single therapy has not merely entered the market; it has redefined it, acting as a powerful catalyst that has already doubled overall sales in 2023 and is expected to capture the lion’s share of the market due to its proven efficacy, strong safety profile, and crucial first-mover advantage.
For decades, HER2-low tumors – those exhibiting low levels of the HER2 protein (classified as IHC 1+ or 2+ with no gene amplification by FISH) – were largely lumped into the “HER2-negative” category.
This meant patients with these cancers, representing a significant proportion of diagnoses (around 63% of breast cancers, 42% of biliary tract cancers, 38% of urothelial carcinomas, and 35% of gastric cancers), often missed out on the benefits of targeted therapies.
Traditional HER2-targeting drugs, like trastuzumab, simply weren’t effective enough at these lower expression levels.
The recognition of HER2-low as a distinct, treatable entity is, therefore, a monumental step forward, expanding the eligible patient pool significantly.
DelveInsight estimates approximately 360,000 target pool cases in the 7MM (United States, Germany, France, Italy, Spain, United Kingdom, and Japan) in 2024, a number set to rise as diagnostic practices evolve and awareness grows.
The magic behind this transformation lies in the innovative design of ADCs.
These aren’t just drugs; they are precision-guided missiles.
An ADC combines a monoclonal antibody, which specifically targets a protein on cancer cells (even if expressed at low levels), with a potent chemotherapy agent.
The antibody delivers the chemotherapy directly to the tumor cells, minimizing damage to healthy tissue and maximizing therapeutic impact.
This “Trojan horse” approach offers a potent solution for cancers that were previously challenging to treat with either conventional chemotherapy or highly specific targeted therapies alone.
ENHERTU’s pioneering approval for HER2-low breast cancer has opened the floodgates, inspiring a fierce, yet highly collaborative, race among pharmaceutical giants.
Companies like AstraZeneca, Daiichi Sankyo, Gilead Sciences, Pfizer (Seagen), Merck, and BioNTech are pouring resources into developing their own cutting-edge ADCs.
The pipeline is robust, featuring promising candidates such as DATROWAY (datopotamab deruxtecan), TRODELVY (sacituzumab govitecan), ifinatamab deruxtecan, BNT323/DB-1303, and disitamab vedotin.
These therapies are not just theoretical; many are in late-stage clinical trials, poised to reshape treatment paradigms in the coming years.
For instance, BioNTech is prioritizing the advancement of DB-1303 for BLA submission in 2025 for advanced endometrial cancer, and Pfizer anticipates a 2026 launch for disitamab vedotin in urothelial carcinoma.
The focus of this therapeutic revolution is largely concentrated on breast and gastric cancers, which are expected to generate the most revenue by 2034 due to the highest levels of clinical development and regulatory authorizations.
However, the ripple effect will undoubtedly extend to other HER2-low indications, as research continues to unravel the complexities of these tumors.
The recent FDA approvals in January 2025 for ENHERTU in HR-positive, HER2-low/ultralow breast cancer and Fast Track Designation for emiltatug ledadotin for advanced HER2-low/negative breast cancer underscore the rapid pace of progress and regulatory support for these novel approaches.
Yet, amidst this wave of optimism, critical challenges persist.
The innovative nature and complex manufacturing of these advanced therapies often translate into high costs, raising concerns about accessibility and affordability across diverse healthcare systems.
Ensuring equitable access will require concerted efforts from policymakers, pharmaceutical companies, and healthcare providers.
Furthermore, while initial clinical results are highly encouraging, ongoing clinical validation and real-world data collection will be crucial to solidify their long-term effectiveness and safety profiles.
The market will also demand increasingly precise diagnostic tools to accurately identify patients who will benefit most from these tailored treatments, reinforcing the growing emphasis on precision medicine in oncology.
In essence, the HER2-low market is more than just a financial opportunity; it represents a profound evolution in our understanding and treatment of cancer.
It’s a testament to the relentless pursuit of scientific innovation, pushing the boundaries beyond simplistic classifications to embrace the nuanced biology of disease.
As these cutting-edge therapies transition from pipeline to patient, they promise not only immense economic growth but, more importantly, a new era of hope for countless individuals battling cancer.
The future of oncology is looking increasingly personalized, and the HER2-low story is a compelling chapter in this unfolding narrative.
