The company announced the receipt of the letter earlier this week, and in a later statement noted its disappointment at the US Food and Drug Administration (FDA) decision to issue the damning document. The new compound, BVF-033, is a new bupropion salt product intended as a once-daily option for the treatment of depression. Biovail believes that BVF-033 could offer a superior safety profile to bupropion hydrochloride, the active ingredient in the company's successful Welbutrin XL product. The compound was also believed to promise advantages through the fact that dissolution of the drug is not accelerated by the presence of alcohol. This is a particular benefit as around 34 per cent of patients drink alcohol while taking their medication, and 61 per cent do not bother to reduce their alcohol intake, according to the company. Biovail's bupropion salt formulation was also intended as a platform for a bupropion combination product, BVF-045. The combination product combines two anti-depressants which between them target serotonin, dopamine and norepinephrine, and could offer benefits in terms of faster onset, better efficacy at lower doses and an improved side effect profile. However, plans for BVF-045 necessarily hinged on approval of BVF-033. The FDA's concerns focused on the design of pharmacokinetic (PK) studies carried out by Biovail, which the agency felt were inappropriate. Biovail, on the other hand, disagrees, and believes that the studies were indeed sufficient. The FDA is requesting that a specific PK study design be followed by Biovail before the product can be considered for approval. According to Nelson Isabel, speaking to US-PharmaTechnologist.com on behalf of the company, carrying out this additional study would take around eight weeks making use of Biovail's in-house contract research organization. However, the class 2 resubmission could then take another six months, adding a total of eight months to the company's time scale for BVF-033. Biovail intends to meet with the FDA as soon as possible to argue the case for the adequacy of the PK studies it has already carried out, and try to avoid this eight month delay to its plans. However, when this meeting will actually take place is still unknown, and could be any time over the next 60 days, potentially drawing out the process even further. Original plans were to launch the BVF-033 product in the fourth quarter of this year, but this timeline looks to have been thrown off by the FDA opinion. Although Biovail is seeing this unexpected hurdle as a "temporary setback" according to Isabel, the company will be keen to launch these new compounds in the $13.5bn US anti-depressant market, particularly as generic competition begins to eat away at sales of certain Wellbutrin products. With no safety of efficacy concerns highlighted by the FDA and Biovail determined to fight its corner regarding the existing PK study data, and the company insists it remains committed to securing approval for BVF-033 through the "most expeditious path possible".