Immunomedics Inc. gained accelerated FDA clearance for Trodelvy (sacituzumab govitecan-hziy) to treat patients with metastatic triple-negative breast cancer (TNBC) who have undergone at least two prior therapies. It’s the first antibody-drug conjugate (ADC) given the go-ahead specifically in relapsed/refractory TNBC and the first anti-Trop-2 ADC bound for the market.

Trodelvy, which was granted breakthrough therapy designation and priority review, moved along faster thanks to the objective response rate (ORR) and duration of response (DoR) turned up by Morris Plains, N.J.-based Immunomedics in a single-arm, multicenter phase II study. Continued approval may be contingent on verifying clinical benefit in the confirmatory phase III experiment called Ascent, recently halted by the independent data safety monitoring committee due to compelling evidence of efficacy across multiple endpoints.

In the phase II effort, Trodelvy yielded an ORR of 33.3% (95% confidence interval [CI]: 24.6, 43.1) and a median DoR of 7.7 months (95% CI: 4.9, 10.8), as determined by local assessment, in 108 adult TNBC patients who had previously received a median of three prior systemic therapies in the metastatic setting (range: 2-10).

Trodelvy’s label carries a black box warning for severe neutropenia and severe diarrhea. The most common adverse reactions occurring in 25% or more of patients included nausea, neutropenia, diarrhea, fatigue, anemia, vomiting, alopecia, constipation, decreased appetite, rash and abdominal pain. The most common grade 3 or 4 adverse events occurring in more than 5% of patients were neutropenia, white blood cell count decreased, anemia, hypophosphatemia, diarrhea, fatigue, nausea and vomiting. Two percent of patients discontinued treatment due to adverse events. There were no deaths related to treatment and no severe cases of neuropathy or interstitial lung disease, Immunomedics noted. The company remains on track to achieve top-line results from the Ascent study by the middle of this year.

Cowen analyst Phil Nadeau acknowledged the black box but said key opinion leaders consulted by his firm “have experience with Trodelvy and find its side effect profile acceptable, so we expect significant adoption.” In a report, he called Immunomedics “undervalued,” and maintained his price target of $30. Shares (NASDAQ:IMMU) were trading at $21.97, up 25 cents. The approval “marks a major milestone for Immunomedics,” and ushers in a new era for the firm as a commercial company, while laying to rest “lingering concerns over a delay due to the recently disclosed manufacturing issues” – a relief to many investors, in his view.

About a year ago, Immunomedics inked a license agreement with Everest Medicines II Ltd., of Shanghai, to develop, register and commercialize the drug in much of Asia outside of Japan. The firm banked an up-front payment of $65 million and will collect $60 million more based on the FDA approval. Included in the deal are potential development, regulatory and sales milestone rewards of $710 million and escalating tiered royalties of 14% to 20% on net sales within a territory that includes greater China and South Korea. Everest is responsible for costs associated with clinical development and commercialization in that territory.

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