By Roxanne Liu and John Miller

BEIJING/ZURICH (Reuters) – Roche said on Wednesday China had approved the import of its Kadcyla drug for breast cancer, another win for the Swiss drugmaker in its second-biggest market where rising demand has helped drive its increased sales and profit.

Kadcyla, which also recently won expanded approval in the United States, Canada and Europe for more breast-cancer patients, is an antibody-drug conjugate (ADC), a class of therapies that combine monoclonal antibodies with cytotoxic chemical that in 2019 picked up momentum with a record number of U.S. approvals.

Over a decade, China has gone from Roche’s 10th biggest market to its second-largest behind the United States, with 4.5 billion Swiss francs ($4.5 billion) in 2018 sales as more of its advanced medicines won Chinese regulators’ favor. The pace has accelerated, with growth in China topping 50% over the first nine months of 2019, about double 2018’s rate.

Roche reports 2019 results next week, and analysts are watching to see whether the pace of Chinese sales growth can be maintained.

Kadcyla, like other ADCs, a type of treatment that combines cancer-tracking proteins with powerful cell toxins, are getting a fresh start as multiple drugmakers including GlaxoSmithKline test a record number of new compounds in people. That’s after some experimental ADCs failed due to the complexity of pairing the right antibody with an appropriate toxic agent.

Kadcyla, approved in 2013 for breast cancer, surpassed $1 billion in annual sales last year, becoming the first ADC to hit blockbuster status.

Also known as ado-trastuzumab emtansine, Kadcyla is approved in China as an adjuvant treatment, or after surgery, in people with HER2-positive early breast cancer who have residual invasive disease after neoadjuvant taxane and treatment based on Herceptin, another Roche drug, the company said in a statement.

Roche’s breast cancer arsenal, including Kadcyla and Herceptin, could be facing strong competition, with biosimilar copies of Herceptin now on the market and December’s U.S. approval of Daiichi Sankyo’s and AstraZeneca’s Enhertu, another ADC drug, well ahead of schedule.

Kadcyla was granted priority review status in June last year by China’s National Medical Product Administration, official records show.

Other ADC products, including Roche’s Polivy, GSK’s Belantamab mafodotin and Abbvie’s Telisotuzumab vedotin, filed applications for clinical trials in China last year. GSK’s drug just won priority U.S. Food and Drug Administration review for multiple myeloma this week, while Polivy won U.S. approval last year for lymphoma.

(Reporting by John Miller in Zurich and Roxanne Liu in Beijing; editing by David Evans)