FRANKFURT (Reuters) - Germany’s health minister Jens Spahn has called for faster adoption of cheaper copies of biotech drugs to treat cancer and autoimmune diseases to reign in rising public healthcare costs.

“Where there is a more affordable alternative at the same quality, we have to use it,” Spahn, who is vying to succeed German Chancellor Angela Merkel as leader of the center-right Christian Democrat party, told daily Handelsblatt.

“Otherwise we won’t be able to sustain the high quality of pharmaceutical supply in Germany,” he said in the interview published on Wednesday.

The paper cited the health ministry as saying that a stringent changeover to biosimilars, which are not exact replicas but are as effective and as tolerable as the original drug, would have saved the healthcare system 279 million euros ($315 million) last year.

Biosimilars will play an increasingly bigger role. Cheaper rival versions of the world’s top-selling drug, AbbVie’s Humira, a remedy against rheumatoid arthritis and other autoimmune diseases with worldwide sales of $18 billion last year, went on sale in Europe last month.

While off-patent chemical drugs are swiftly replaced by cheaper generic copies in Germany’s healthcare system, the transition from original biotech drugs to biosimilars is slower and the rate varies between regional states.

In Germany, Europe’s biggest drug market, the decentralized system leaves physicians free to prescribe the brand they deem best. But German doctors are also legally bound to observe cost efficiency and could be challenged if they simply carry on prescribing the more expensive original medicine.

According to German lobby group Pro Biosimilars, biosimilar adoption rates based on the number of treatments in Germany have varied from below 10 percent for insulin glargine to over 70 percent for filgrastim, which treats side effects of chemotherapy.

More recently, biosimilars of rheumatoid arthritis drugs have seen adoption rates of above 50 percent.