Starting in 2011, the global market for branded atypical antipsychotic drugs will experience significant erosion as a number of leading treatments begin to lose patent exclusivity and, as a result, the bipolar disorder drug market will have lost more than $1 billion in value by 2018, according to a new report.

The market will be constrained over the next several years by the patent expiries and subsequent generic erosion of a number of key antipsychotic agents including AstraZeneca’s Seroquel (quetiapine fumarate), Eli Lilly’s Zyprexa (olanzapine), Bristol-Myers Squibb/Otsuka’s Abilify (aripiprazole) and Pfizer’s Geodon (ziprasidone), according to the study, from Decision Resources. As a result, sales of these four products alone in the US, France, Germany, Italy, Spain, UK and Japan will decline from more than $4 billion last year to just under $3 billion by 2018, and the entire market for bipolar disorder drug treatments will fall from $6.3 billion to around $5 billion over the period, it says.

Moreover, patent expiries of branded antidepressants that include Wyeth’s - now Pfizer’s - Effexor XR (venlafaxine), Eli Lilly’s Cymbalta/Xeristar (duloxetine) and Forest/Lundbeck’s Lexapro/Cipralex (escitalopram) will further constrain the market, according to the report.

However, despite the overall decline, Decision Resources is also forecasting modest growth in sales of bipolar disorder therapies in Japan and European markets during 2008-2018. Growth in these markets will be due in part to the continued uptake of atypical antipsychotics and an increasing drug-treated population for the indication, according to Dr Alana Simorellis, an analyst with the firm.

The study also suggests that expanded labeling for AstraZeneca’s Seroquel and Seroquel XR (extended release) to include bipolar maintenance and bipolar depression, as well as the potential approval of Dainippon Sumitomo Pharma Co’s lurasidone for bipolar depression, will serve to differentiate these therapies from other atypical antipsychotics. In September, Seroquel and Seroquel XR were approved in the European Union (EU) for a new indication, the prevention of recurrent bipolar disorder, making the two drugs the only treatments to be approved in the EU for all phases of the condition.

And in August, following the positive results released from PEARL 2 (Programme to Evaluate the Antipsychotic Response to Lurasidone) – a worldwide Phase III clinical development programme for the drug involving more than 2,000 patients – Dainippon Sumitomo Pharma's chief executive Masayo Tada said the firm planned to submit its New Drug Application (NDA) filing package for lurasidone to the US Food and Drug Administration (FDA) early in 2010.

Bipolar depression is difficult to treat, and there is substantial market opportunity for therapies that address this market segment, the report suggests.