Elahere Drug Interactions: What to Avoid and What to Tell Your Doctor

Like any medication, Elahere (mirvetuximab soravtansine-gynx) can interact with other drugs. Because Elahere contains a potent chemotherapy payload (DM4) that is broken down by enzymes in your body, certain medications can increase or decrease its concentration in your blood — potentially making it more toxic or less effective. Here's what you need to know about Elahere drug interactions before and during treatment.

How Do Drug Interactions Affect Elahere?

The key interaction mechanism involves the DM4 payload — the chemotherapy drug inside Elahere. DM4 is a substrate of an enzyme called CYP3A4, which is responsible for metabolizing (breaking down) many drugs in the liver. Drugs that affect CYP3A4 activity can change how much free DM4 circulates in your body:

CYP3A4 inhibitors slow down the breakdown of DM4 → DM4 levels increase → greater risk of side effects (toxicity)

CYP3A4 inducers speed up the breakdown of DM4 → DM4 levels decrease → potential loss of effectiveness

Strong CYP3A4 Inhibitors: Use With Caution

The Elahere prescribing information specifically warns about strong CYP3A4 inhibitors. These medications can significantly increase unconjugated DM4 exposure and may increase the risk of adverse reactions, including ocular toxicity, peripheral neuropathy, and other side effects. Examples of strong CYP3A4 inhibitors include:

Antifungals: ketoconazole, itraconazole, voriconazole, posaconazole

Antibiotics: clarithromycin (Biaxin), telithromycin

HIV medications (protease inhibitors): ritonavir, atazanavir, darunavir, lopinavir, nelfinavir, saquinavir, tipranavir, indinavir

Other drugs: conivaptan, mifepristone, cobicistat (a pharmacokinetic booster in HIV regimens)

If you are taking any of these medications, tell your oncologist before starting Elahere. They may recommend monitoring more closely, adjusting your dose, or using an alternative drug for the interacting medication.

Strong CYP3A4 Inducers: Possible Reduced Effectiveness

Drugs that strongly induce CYP3A4 may reduce DM4 levels, potentially reducing Elahere's effectiveness. Examples include:

Rifampin (used for tuberculosis and other infections)

Phenytoin, carbamazepine, phenobarbital (seizure medications)

St. John's Wort (herbal supplement — very important to disclose)

Etrasimod: Avoid Combination

Etrasimod (Velsipity), a sphingosine-1-phosphate receptor modulator used for ulcerative colitis, should be avoided with Elahere due to additive immunosuppressive effects. Because the combination's safety has not been studied, prescribers are advised to avoid coadministration during and in the weeks following etrasimod use.

What About Supplements and Herbal Remedies?

Many patients take supplements or herbal remedies alongside cancer treatment without telling their doctor. This can be risky. St. John's Wort is a well-known CYP3A4 inducer that can significantly reduce drug levels of many cancer medications, including Elahere's DM4 payload. Other supplements like grapefruit (a mild CYP3A4 inhibitor) and turmeric (curcumin) can also affect drug metabolism.

Be honest with your oncologist and pharmacist about all supplements, vitamins, and herbal products you use.

Medications That Are Generally Safe With Elahere

Most medications are unlikely to significantly interact with Elahere, since its interaction profile is primarily driven by CYP3A4 and DM4 metabolism. Many common medications — including most blood pressure drugs, thyroid hormones, antidepressants (most SSRIs), and low-potency antifungals (like fluconazole, which is only a moderate CYP3A4 inhibitor) — can generally be used with Elahere with appropriate monitoring.

However, this is not a complete list. Always have your oncologist and pharmacist review your full medication list before starting Elahere and whenever new medications are added.

Special Situations: Pregnancy and Breastfeeding

Pregnancy: Elahere contains DM4, a genotoxic compound, and can harm an unborn baby. Verify pregnancy status before starting. Use effective contraception during treatment and for 7 months after the last dose.

Breastfeeding: Do not breastfeed during Elahere treatment and for 1 month after the last dose. It is unknown whether Elahere or DM4 is present in human milk.

Related: Elahere Side Effects: What to Expect and When to Call Your Doctor.

Need help finding an infusion center that administers Elahere? Visit medfinder to locate facilities near you.