For Decades, Collateral Damage Was the Price of Cancer Treatment. That’s Finally Changing.

For generations, treating cancer has relied on a pretty brutal calculus: hit the body hard and hope the cancer dies first. Traditional chemotherapy is essentially a scorched-earth strategy. It works, but at a massive cost—wrecking the heart, gut, and nervous system along with the tumour.

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For decades, researchers have chased a deceptively simple question: What if we could send the drug only where it’s actually needed?

Antibody-drug conjugates, or ADCs, are the most promising answer we’ve found so far. And looking at what’s happening in clinics right now, we’re likely only scratching the surface of what they can do.

The question researchers have been asking for decades is deceptively simple: what if the drug only went where it was needed?

Antibody‑drug conjugates — ADCs — are the most compelling answer that question has produced so far. And what’s happening in the clinic right now suggests we’re only beginning to understand what they can do.

Q: What is an ADC, and why does it matter that it’s different?

A:Think of it as a three‑part precision delivery system.

A monoclonal antibody — engineered to recognise a specific marker on cancer cells — is chemically linked to a highly potent chemotherapy drug via a “tether” called a linker. The antibody acts as the GPS. The linker acts as the safety pin. The drug is the payload that gets released only once the whole package is inside the cancer cell.

What makes this genuinely significant isn’t just the targeting. It’s the class of drugs ADCs make possible. Many ADC payloads are so toxic they would be lethal if given freely into the bloodstream. Guided by an antibody, they become viable — and in some cases, transformative.

As of 2025, 15 ADCs have been approved globally, covering more than 15 tumour types. A decade ago, that number was in single digits. The pipeline currently holds over 100 candidates in active clinical trials.

The technology has moved from promising concept to mainstream oncology faster than almost anyone predicted.

Q: If the idea is so elegant, why isn’t it straightforward?

A: Because tumours are not cooperative.

Three problems come up again and again in the clinical data — and each one has forced a rethink of what “good ADC design” actually means.

Tumours are not uniform. Even within a single patient’s cancer, cells can express very different levels of the surface marker the ADC is designed to find. Target some cells, miss others — and the ones that escape drive relapse.

Getting deep into a tumour is harder than it sounds. Dense tumour tissue can physically block ADCs from penetrating beyond the outer layer. If the drug can’t reach the centre, it can’t finish the job.

And here’s the counterintuitive one: for years, the guiding principle was bind as tightly as possible. Tighter grip, more specific delivery. That made obvious sense — until clinical data showed that extremely high‑affinity antibodies can get trapped at the first cancer cells they encounter and never distribute deeper into the tumour.

A new approach called HALA antibodies — high‑avidity, low‑affinity — deliberately flips that logic. Moderate binding strength, better tumour penetration, less risk of sticking to healthy tissue that expresses low levels of the target. It’s a design shift that would have seemed counterproductive a decade ago.

The field isn’t just building more powerful missiles. It’s learning to build smarter ones.

Q: What does the clinical data actually tell us about where this is headed?

A:The most telling signal isn’t any single trial result. It’s where in the treatment journey ADCs are now being used.

Early ADCs were largely reserved for patients who had exhausted every other option — a last resort. What strong clinical data has done is push ADCs progressively earlier in treatment, in some cases into first‑line and even pre‑surgical settings.

The DESTINY‑Breast04 trial — testing trastuzumab deruxtecan in HER2‑low breast cancer — is the clearest example. It didn’t just show survival benefit in a difficult‑to‑treat population. It redrew the boundaries of who qualifies for HER2‑targeted therapy entirely, opening the door for a much larger group of patients who were previously considered ineligible.

That pattern — ADCs expanding who can be treated, not just how — is repeating across tumour types.

And beyond oncology, early work is exploring ADCs in autoimmune disease, infectious disease, and fibrosis. The antibody‑linker‑payload platform is not inherently cancer‑specific. Oncology is essentially building the infrastructure for something much broader.

The older treatment model was: find the most powerful drug possible, then manage the collateral damage.

The model being written now is: understand the biology well enough to send the right thing, to the right place, at the right time.

ADCs didn’t change what we were trying to do. They changed what we believed was possible.

Sources: Cell (2026); Med (2025); Frontiers in Pharmacology (2023); PMC Cancer Therapy Review (2025); Dana‑Farber Cancer Institute (2024)