An Immunomedics therapy for an aggressive form of breast cancer won FDA approval on Wednesday. It’s the company’s first regulatory nod, and it covers a product expected to become a blockbuster seller.
Morris Plains, NJ-based Immunomedics (NASDAQ: [[ticker:IMMU]]) developed the drug, sacituzumab govitecan (Trodelvy), as a treatment for treat triple negative breast cancer. This form of the disease is not fueled by the hormones estrogen or progesterone or by the HER2 protein, and therefore doesn’t respond to hormone therapy or HER2-targeting drugs.
About two of every 10 breast cancer diagnoses worldwide are triple negative, according to the FDA. The regulator approved the Immunomedics drug for patients whose cancer has not responded to at least two earlier treatments and has spread. The company estimates that this market is between 8,000 and 9,000 patients. The drug is an antibody drug conjugate (ADC), a therapy made by attaching a cancer-killing compound to an antibody that homes in on cancer cells. This approach is intended to spare healthy tissue by providing a targeted strike to tumors.
The Immunomedics drug specifically targets Trop-2, a protein on the surface of many solid tumors. The company designed its drug to bind to that protein and deliver its therapeutic payload, a chemical compound toxic to cancer cells. That compound, SN-38, is a topoisomerase inhibitor that works by causing damage to the DNA of cancer cells. The FDA decision makes sacituzumab govitecan the first approved ADC that binds to Trop-2.
Sacituzumab govitecan nearly ended up in the hands of Seattle Genetics (NASDAQ: [[ticker:SGEN]]). Three years ago, the Bothell, WA-based ADC specialist reached a deal to acquire the global rights to the drug. But Immunomedics shareholder opposition, litigation, and a change in the New Jersey company’s board of directors unwound the agreement. Immunomedics kept its lead cancer drug and continued its development.
Approval of the Immunomedics drug Wednesday comes more than a month ahead of the June 2 target date for a regulatory decision, but it’s actually later than the company hoped. The company initially submitted its application in 2018. Early last year, the FDA rejected the drug due to manufacturing problems. Immunomedics resubmitted its application last November.
The FDA reviewed the Immunomedics drug on an accelerated basis, a pathway reserved for therapies addressing an unmet medical need. The decision was based on a single-arm Phase 2 study enrolling 108 patients. Of those patients, 33.3 percent showed a response to the treatment. The median duration of that response was 7.7 months.
The most common side effects observed in the study included nausea; neutrophenia, a deficiency of a type of white blood cells called neutrophils; diarrhea; fatigue; and anemia. Two percent of patients dropped out of the study due to side effects. There were no deaths reported in connection with the treatment.
The drug’s label carries a boxed warning flagging the risk of neutropenia and diarrhea that can be severe. The label advises physicians to monitor a patient’s blood cell counts and also consider granulocyte-colony stimulating factor, a therapy that stimulates the bone marrow to produce white blood cells and stem cells. The FDA adds that anti-infective treatment should be started in patients who develop a fever when their white blood cell counts are abnormally low.
Speaking on a conference call, Chief Medical Officer Loretta Itri said that no patients dropped out of the study due to neutropenia or diarrhea. She added that the warning on the drug’s label is similar to the warnings for other topoisomerase inhibitors.
Drugs reviewed on an accelerated basis still need to show additional clinical data in order to keep their approval. Two weeks ago, Immunomedics announced that a Phase 3 clinical trial that enrolled more than 500 patients is stopping early after an independent committee reviewing the study’s data found that the drug provided “compelling evidence of efficacy.” Behzad Aghazadeh, the company’s executive chairman, said on the call that the data from the Phase 3 study are being compiled and analyzed, and preliminary results are expected to be ready by the middle of this year.
Immunomedics is preparing to make its drug available through specialty distributors and specialty pharmacies. Chief Commercial Officer Brendan Delaney said that the price of the drug is $2,012.50 for a single 180 mg vial. How much drug is needed will depend on a patient’s weight and the duration of treatment. But Delaney said that the projected wholesale cost, before discounts and rebates, is between $101,000 and $119,000.
Meanwhile, Immunomedics isn’t stopping at triple negative breast cancer. The company says its drug is currently being evaluated as a potential treatment for eight hard-to-treat solid cancers.
Public domain image by Kevin Janes of the University of Virginia, via the National Cancer Institute
