Roche's cancer drug Kadcyla, an expected superstar that is pegged to assume the mantle of Herceptin in later years, has moved forward in Europe where Friday it was recommended for approval. The FDA signed off on it February.

The drug combines Roche's ($RHHBY) antibody drug Herceptin (trastuzumab) with drug-conjugate technology from ImmunoGen ($IMGN). Kadcyla has shown some advantages over blockbuster Herceptin, so it could pick up some of the sales Herceptin will lose when biosimilar competition is mounted against some of Roche's older cancer drugs. The drug also carries a price that is more than twice that of Herceptin, a reported $9,800 a month for the injection, compared to the $4,500 for Herceptin. The explosive sales of the drug, 83 million Swiss francs ($91 million) in its first quarter, have analysts suggesting peak sales could range anywhere from $2 billion to $5 billion annually.

Despite the price, the Committee for Medicinal Products for Human Use (CHMP) in Europe recommended approval. The European Medicines Agency (EMA) usually follows up in a couple of months with endorsements of those recommendations.

The drug was credited by some market-watchers with supercharging Roche's financial results so far this year. Roche in July reported a 10% hike in profits for the first half of the year. That was on sales that beat analyst estimates at about $8 billion. The results were also boosted by other drugs in Roche's cancer portfolio, like Rituxan, but Kadcyla was the one analysts zeroed in on.

Roche faces biosimilar competition in coming years for Herceptin, yet Kadcyla has shown benefits over the former drug in clinical trials and that could help Roche maintain an edge over rivals and hold onto much of the impressive sales its cancer drugs have produced over the years. It offers a novel way to treat HER2-positive metastatic breast cancer and in trials delivered a 32% reduction in the risk of death compared with the standard-of-care.