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Seattle Genetics preps filing next year for oral HER2 drug

Company has positive phase 3 data to support filings

Seattle Genetics

Seattle Genetics has positive phase 3 data in hand for its orally-active HER2 inhibitor tucatinib in breast cancer that the company says will support regulatory filings in the first quarter of 2020.

The HER2CLIMB trial evaluated tucatinib as an add-on therapy to Roche’s anti-HER2 antibody Herceptin (trastuzumab) plus Xeloda (capecitabine), and it found that the new drug achieved a 46% reduction in the risk of disease progression or death compared to the two Roche drugs given alone.

Herceptin plus Xeloda is a standard regimen for HER2-positive breast cancer in patients previously treated with Herceptin and Roche’s other HER2-targeting drugs Perjeta (pertuzumab) and Kadcyla (ado-trastuzumab emtansine).

Tucatinib also met two secondary objectives in the trial, with a 34% reduction in the risk of death, and a 52% fall in the risk of disease progression or death in patients whose cancer had metastasised into the brain at the time they were enrolled in the study.

The new data caused a 15% spike in Seattle Genetics’ share price as investors contemplated a possible approval for tucatinib next year and the potential for the new drug to piggyback on the massive success of Roche’s HER2 franchise, which contributed almost $11bn to its top line last year, around 19% of total sales.

Around $7bn of that total came from Herceptin, which is starting to feel the effects of biosimilar competition, but that shouldn’t affect tucatinib if it claims approval as a triple therapy alongside trastuzumab/capecitabine.

Analyst Andrew Berens at SVB Leerink said Seattle Genetics’ strategy with tucatinib could lead to “significant commercial success”, given the tough challenge of improving on Herceptin’s efficacy in this setting, and could become a $400m-plus product.

He also suggested the data on tumours that have spread to the brain could provide a route to use of the drug earlier on in the treatment pathway in patients with metastases.

The company has already started a phase 3 trial that aims to support earlier use of tucatinib. HER2CLIMB-02 will compare tucatinib to placebo in combination with Kadcyla in HER2-positive breast cancer patients who have received prior treatment with a taxane and Herceptin.

The data is a further boost to Seattle Genetics, which has been on a roll lately with positive results for its antibody-drug conjugate enfortumab vedotin, now filed for approval as a later-line bladder cancer treatment after checkpoint inhibitors and chemotherapy.

The company licensed tucatinib from Cascadian Therapeutics last year in a deal valued at $614m, and on the face of the efficacy data it is looking like a good deal. Competition in the HER2 category is heating up though, with a new antibody-drug conjugate from Daiichi Sankyo and AstraZeneca – trastuzumab deruxtecan – angling for approval in the US in the second quarter of 2020.

One potential area of concern is a potential safety signal in the HER2CLIMB data, with around 5% of patients taking tucatinib exhibiting an increase in two liver enzymes that can point to liver damage, versus 0.5% of the control group.

On the whole though tucatinib was “generally well tolerated with a manageable safety profile” said Seattle Genetics, and adverse events leading to discontinuations were “infrequent” in both treatment arms.

Article by
Phil Taylor

22nd October 2019

From: Regulatory



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