Nov 15 (Reuters) - Drugmaker Immunogen said on Tuesday it would sell its newly approved ovarian cancer drug at a list price of $6,220 per vial and start shipping it "in a matter of days".

Most patients will receive three to four vials of Elahere per treatment cycle, putting the cost at about $18,500 to $25,000 a cycle, Immunogen Chief Executive Mark Enyedy said on a conference call.

Elahere will be administered once in every 21 days and the recommended dose is of 6 mg/kg based on a patient's weight.

BMO Capital Markets analyst Etzer Darout said the list price was consistent with other marketed drugs in the same class.

Elahere belongs to a class of cancer therapies known as antibody-drug conjugates, which are so-called "guided missile" that target and kill tumor cells while sparing healthy cells.

Other antibody drug conjugates include AstraZeneca's Enhertu, Seagen's Padcev and Gilead's Trodelvy.

"When you look at other marketed antibody drug conjugates, Elahere is (priced) relatively in line in terms of the price per month of $18,500 to $25,000 range," Darout said.

Gilead's breast cancer drug

Trodelvy

, which is given twice in a 21-day treatment cycle, has a U.S. list price of $2,188 per vial. Dosage of Trodelvy varies based on a patient's weight and the recommended dosage is 10mg/kg.

Late on Monday, Immunogen said the U.S. Food and Drug Administration had approved Elahere for treatment of platinum-resistant ovarian cancer in adults. The drug carries a black box warning for potential damages to patients' eyes including impairment of vision and pain.

Shares of the Massachusetts-based company rose initially before falling 10%, which Darout said could be driven by skepticism around Elahere's commercial opportunity. (Reporting by Bhanvi Satija in Bengaluru; Editing by Shinjini Ganguli and Maju Samuel)