Padcev is neither traditional chemotherapy nor immunotherapy. It belongs to a newer class of cancer drugs called antibody-drug conjugates, or ADCs, which combine elements of both approaches into a single treatment. The FDA classifies Padcev as a “Nectin-4-directed antibody and microtubule inhibitor conjugate,” and it’s approved for treating advanced bladder cancer (urothelial carcinoma).
How Padcev Actually Works
An antibody-drug conjugate is essentially a guided missile. It has two components: an antibody that seeks out cancer cells, and a potent cell-killing agent that’s attached to it. In Padcev’s case, the antibody locks onto a protein called Nectin-4, which sits on the surface of bladder cancer cells. Once the antibody attaches, the entire drug gets pulled inside the cancer cell, where the cell-killing payload is released.
That payload, called MMAE, destroys the cell’s internal scaffolding (microtubules), which prevents it from dividing and ultimately kills it. This mechanism is similar to how certain chemotherapy drugs work. The key difference is delivery: traditional chemo circulates throughout your entire body, attacking fast-growing cells wherever it finds them. Padcev directs its toxic payload specifically to cells displaying Nectin-4, which reduces collateral damage to healthy tissue.
Padcev also has a “bystander effect.” Once the drug kills a Nectin-4-positive cancer cell, the released payload can leak into neighboring cancer cells that don’t even have Nectin-4 on their surface, killing those too. This makes it effective against tumors with mixed cell populations.
Why It’s Often Paired With Immunotherapy
While Padcev itself is not an immunotherapy drug, it’s frequently given alongside one. In December 2023, the FDA approved Padcev in combination with pembrolizumab (Keytruda), a well-known immunotherapy, as a first-line treatment for advanced or metastatic urothelial cancer. National guidelines now list this combination as the single preferred option for patients starting treatment.
The results from the large clinical trial behind this approval were striking. Patients receiving the Padcev-plus-Keytruda combination lived a median of 33.8 months, compared to 15.9 months for patients on standard chemotherapy. Progression-free survival, the time before the cancer started growing again, roughly doubled: 12.5 months versus 6.3 months. This pairing works because the two drugs attack cancer through different pathways. Padcev directly poisons cancer cells, while Keytruda helps the immune system recognize and fight them.
What Treatment Looks Like
Padcev is given as an intravenous infusion lasting about 30 minutes. The standard schedule is three infusions per 28-day cycle, on days 1, 8, and 15, with a week off before the next cycle begins. Treatment continues as long as the cancer responds and side effects remain manageable.
One practical advantage: no biomarker testing is required before starting Padcev. The protein it targets, Nectin-4, is found on over 96% of urothelial cancer tumors, so testing for it isn’t necessary. This is different from many targeted therapies and immunotherapies that require genetic or protein testing to determine eligibility.
Common Side Effects
Because Padcev carries a chemotherapy-like payload, its side effects overlap with both chemo and targeted therapy. The most common ones reflect its unique mechanism.
Peripheral neuropathy, tingling, numbness, or weakness in the hands and feet, affects about 53% of patients receiving Padcev alone and 65% when combined with Keytruda. Most cases involve sensory changes rather than muscle weakness, but it’s the side effect most likely to require dose adjustments.
Skin reactions are also frequent, occurring in 56% of patients on Padcev alone and 72% on the combination. These can range from mild rashes to more serious reactions, and your care team will monitor for them closely.
Blood sugar elevation is another concern. About 14% of patients on Padcev alone develop elevated blood sugar, with 7% reaching levels considered severe. When Padcev is combined with Keytruda, some degree of blood sugar increase shows up in about 74% of patients on lab work, though most cases are mild. Patients with diabetes or prediabetes need particularly close monitoring.
Where ADCs Fit in Cancer Treatment
Antibody-drug conjugates like Padcev represent a growing category that blurs the old chemotherapy-versus-immunotherapy line. They use the precision targeting of antibody-based therapy to deliver a traditional cell-killing agent directly where it’s needed. In practice, oncologists sometimes informally refer to ADCs as a form of targeted therapy, though they carry side effect profiles that can resemble both chemo and immunotherapy depending on their specific design.
For bladder cancer specifically, Padcev has shifted the treatment landscape significantly. Before its approval, platinum-based chemotherapy was the backbone of treatment for advanced disease. Now, the Padcev-Keytruda combination has become the preferred first-line approach, with traditional chemo regimens listed as alternatives for patients who can’t receive the newer option.