Generic drugs are expected to take over the antiviral drugs market, especially for HIV medication, as a series of patent expiries open opportunities for ambitious companies to seize huge revenues, says a new report.

An increase in the patient population and reforms to government polices will work together to encourage the rise of generic drug power, according to the study, from GBI Research.

Such government actions will include the requirement for prior authorisation before branded drugs that have generic alternatives can be dispensed, while further incentives are available from pharmacy benefit manager (PBM) companies for dispensing generic drugs. These kinds of regulatory changes and financial benefits could act as significant drivers of the market during the forecast period, says GBI.

While it is estimated that, in 2010, generics accounted for 18.9% of the global antivirals market, their share is expected to reach 29.2% by 2018. This will be largely due to a series of patent expiries set to hit the antivirals market which will act to raise the value of generic antiviral drugs to over $9 billion by 2018.

Generics in the HIV market in particular accounted for an estimated majority market share of 46% in the total generic antivirals market during 2010. HIV generics are expected to create a boom in the market, due to the loss of patent exclusivity for key antiviral drugs.

The generics market is currently dominated by products such as zidovudine, didanosine, stavudine and lamivudine. However, many major patents are set to expire during the forecast period, including those for Bristol-Myers Squibb's Sustiva (efavirenz) and Abbott Laboratories' Kaletra ((lopinavir/ritonavir) in 2013, Johnson & Johnson's Prezista (darunavir) in 2014, and major nucleoside reverse transcriptase inhibitors (NRTIs) such as GlaxoSmithKline's Trizivir (abacavir/lamivudine/zidovudine), GSK's Epzicom (lamivudine/abacavir) and Gilead Sciences' Emtriva (emtricitabine) in 2016.

By 2018, billions of dollars' worth of industry revenue will be lost from the expiry of these brand-name products, and the race will be on for generics manufacturers to create new "superstar" drugs to make the most of this unmet need in the market, says GBI. Sales of generics within the antiviral market are forecast to rise at a compound annual growth rate (CAGR) of 10.5% during 2010-18, it adds.

The report also notes that, in December 2011, Teva launched onto the US market a generic version of GSK and Pfizer's ViiV Healthcare joint venture's combination product Combivir (zidovudine/lamivudine), indicated in combination with other antiretroviral agents for the treatment of HIV-1 infection. Combivir's annual sales reached approximately $556 million in 2010, it notes.