Chemotherapy for the Modern Age: Antibody–Drug Conjugates (ADCs)
By Pharmacist Li-Hua Fang, Department of Pharmacy
Antibody–drug conjugates sound like something from a sci-fi screenplay: a guided missile that homes in on a cancer cell, unloads a lethal warhead, and spares the surrounding terrain. Four decades of laboratory setbacks and breakthroughs have turned that vision into everyday oncology.
From Bold Idea to Hospital Drip
The concept surfaced in the early 1980s when researchers asked whether the immune system’s own homing beacons, antibodies, could ferry cytotoxic payloads directly into tumours. Prototype ADCs stumbled over unstable chemical linkers and underwhelming trial results, yet every failure prompted smarter chemistry. The breakthrough came with linkers that snap only inside the target cell and with far more potent toxins. Those refinements ushered in the second-generation ADCs now changing cancer care.
Five Marketed ADCs That Rewrote the Playbook
Brentuximab Vedotin (Adcetris) targets CD30 on Hodgkin and anaplastic large-cell lymphomas, delivering higher response rates and longer survival than standard chemotherapy.
Trastuzumab Emtansine (Kadcyla) fuses the HER2 antibody trastuzumab with the toxin emtansine, giving patients with HER2-positive breast cancer a potent option when earlier HER2 therapy has failed.
Trastuzumab Deruxtecan (Enhertu) pushes HER2 targeting further. Its “bystander effect” means the released toxin also kills neighbouring tumour cells that may lack HER2, a boon in heterogeneous cancers. In 2020 clinical trials showed dramatic tumour shrinkage and durable control in heavily pre-treated HER2-positive breast and gastric cancers. By 2022 the FDA had expanded approval to HER2-low breast cancer, a subtype previously overlooked.
Enfortumab Vedotin (Padcev) zeroes in on Nectin-4, highly expressed in advanced bladder cancer, giving patients an effective therapy where few existed.
Sacituzumab Govitecan (Trodelvy) binds to Trop-2 and has become a lifeline for triple-negative breast cancer, one of the most aggressive forms, significantly extending survival.
Why ADCs Can Beat Classic Chemotherapy
Because the antibody delivers the toxin straight to its mark, healthy cells suffer far less collateral damage, so side-effects are milder even when the payload itself is exceptionally potent. ADCs can also out-flank drug resistance: Trastuzumab Emtansine works after tumours stop responding to trastuzumab alone.
Flexibility is another edge. Scientists are building new conjugates with stronger toxins, smarter linkers, or even dual antibodies that hit more than one tumour marker at once. Over 100 ADCs are now in clinical trials, poised to tackle cancers that have long defied treatment.
Looking Ahead
The next challenge is to make these missiles still more “intelligent”—kinder to normal tissue, deadlier to cancer, and adaptable to the quirks of each tumour’s genetics. With so many candidates in the pipeline, the ADC field is likely to broaden far beyond today’s indications and bring hope to patients who, until now, have had none.