Combined sales of seven emerging drugs used in the treatment of breast cancer will reach close to $5 billion in seven major markets by 2019, a new report forecasts.

Experts consulted for their views on currently-emerging therapies for breast cancer are particularly enthusiastic about agents in the Poly ADP-Ribose Polymerase (PARP) inhibitor drug class, says the study, which is published by research firm Decision Resources (DR).

Iniparib, Sanofi-Aventis’s treatment in this class, has the potential to achieve blockbuster peak-year sales in excess of $1 billion in the seven markets covered – the USA, France, Germany, Italy, Spain, the UK and Japan – forecasts the report, which also notes that other key PARP inhibitors currently in development include AstraZeneca’s olaparib and Abbott Laboratories’ veliparib.

DR also projects that sales of agents targeting HER2-positive breast cancer will increase almost $2 billion by 2019, and that this growth will be fueled by the increasing uptake of Roche/Chugai’s Herceptin (trastuzumab) and GlaxoSmithKline’s Tykerb/Tyverb (lapatinib), plus the approval of three new HER2-targeted therapies - Roche/Genentech/Chugai’s trastuzumab-DM1, Roche/Chugai’s Omnitarg (pertuzimab) and Pfizer’s neratinib.

Roche/Genentech/Chugai’s Avastin (bevacizumab) has won a substantial share of the market, particularly in the metastatic triple-negative and metastatic HR-refractory treatment settings where there are currently few effective therapies. However, on July 20 this year, the drug’s future in this indication was cast into doubt after the US Food and Drug Administration (FDA)’s Oncologic Drugs Advisory Commission (ODAC) recommended that the agency should rescind its conditional approval for use in the treatment of first-line metastatic HER2-negative breast cancer. The FDA had granted accelerated approval for Avastin for this indication in February 2008, contingent on additional positive results from ongoing clinical trials.

Then in September, the European Medicines Agency (EMA)’s Committee for Medicinal Products for Human Use (CHMP) announced that it had started a review of Avastin’s benefits and risks, in view of the results of a study submitted by Roche in support of an application for the drug’s use in the treatment of breast cancer in combination with anthracycline-based or capecitabine cytotoxic chemotherapy.

“In comparison to results of previous studies, this study points to inconsistencies between different trials relevant for the currently-approved breast cancer indication, particularly in terms of efficacy,” said the CHMP.

However, on October 18, the National Comprehensive Cancer Network (NCCN), an alliance of 21 of the world’s leading cancer centres, announced that its guidelines panel for breast cancer had affirmed its existing recommendation for Avastin in combination with Bristol-Myers Squibb’s Taxol (paclitaxel), and this is a positive sign for Roche, comments Decision Resources analyst Niamh Murphy.

Nevertheless, “even in the event that Avastin manages to hang on to a first-line metastatic breast cancer label, its sales - which surpassed $1 billion for breast cancer alone in 2009 in the world’s major markets - will plummet over the next several years,” Dr Murphy forecasts.

“By 2019, sales of Avastin in breast cancer will drop to $350 million as a result of oncologists’ diminishing confidence in the agent, increased prescribing and reimbursement restrictions and competition from emerging therapies, most notably, iniparib and Eli Lilly’s VEGF inhibitor, ramucirumab,” she concludes.