The US Food and Drug Administration's (FDA) issuance of approvable letter for the New Drug Application (NDA) submitted by Dr Reddy's Laboratories Ltd is a "sizeable" positive for DRL even as the issues in amlodipine were getting complicated of late, an international analyst claimed here.

An Indian analyst said he did not agree with the assessment. "It reinforces that DRL has taken care to put forth a solid case to the regulator, ie., US FDA which appears approvable, prima facie. The more important issue of product labelling has still to be debated besides the patent challenge with Pfizer. However, I think specific chemistry manufacturing controls would have been covered well by DRL. Nevertheless, this is a decent first attempt by an Indian company in an unknown 505(b)(2) arena," he said.

The final approval is expected after the end of the litigation between DRL and Pfizer. According to the international analyst, "There is no clarity on whether DRL gets the three-year exclusivity." While DRL expects the "summary judgement" in end 1Q 2003 in the lower court, the analyst says he expects Pfizer to appeal even if it loses this case.

Though DRL CEO G V Prasad expects to launch the product on August 26, 2003, the analyst expects litigations to be prolonged and maintains that an "earliest launch" by DRL will be in the first quarter of 2004 and there could be a "practical exclusivity" for around six quarters on amlodipine maleate. However, the "administrative error" by Pfizer in not suing Mylan for the latter's amlodipine besylate could impinge on the upsides for DRL, says the international analyst.

While this product is similar to Pfizer's Norvasc (which is amlodipine besylate - a cardiovascular drug with sales of $1.27 billion and global sales of $ 2.78 billion in the first three quarters this calendar), it is not AB-rated (ie., fully bio-equivalent) and hence not generically substitutable to Norvasc.

While the international analyst believes that there is "little likelihood" of getting this exclusivity, there is a possibility of getting "practical exclusivity" of four to six quarters for maleate as most generic companies are working on doing equivalence to amlodipine besylate (which will be AB rated to Norvasc) rather than amlodipine maleate (AB rated to DRL's product).

Working on getting equivalence to DRL's maleate, filing with US FDA and getting approvals will allow "practical exclusivity" for DRL. DRL's motion for summary judgment is scheduled to be heard in mid-December 2002.
While the main contention between Pfizer and DRL is a seemingly simple issue, legally it may take some time to resolve. Pfizer 's '909 patent expires on February 25, 2003, and it was given an extension till July 2006. As per DRL, patent extensions are only for products that are in the market-place.

However, as Pfizer is only marketing besylate salt, the patent extension is only valid for besylate salt and not for the maleate salt. Pfizer seems to state that US FDA has delayed approving the basic amlodipine product and hence the patent extension for this basic substance is warranted.

The "administrative error" stated by Pfizer last week also complicates issues, says the international analyst. Last week, Pfizer and Mylan stated that Pfizer didn't sue Mylan on the latter's para IV fling for amlodipine besylate till more than 45 days after receiving the notice. Due to this delay, there is no bar on USFDA approving the product. USFDA gives the approvals based on the product quality and bio-equivalence to the patent-holder's product.

Thus there is a possibility that Mylan could get the final USFDA approval much before the end of the 30-month period. There is a possibility that Mylan could launch its generic "at risk" as soon as it gets the final US FDA approval.

This launch would significantly impinge on the upsides from section 505 (b) (2) filing of DRL for its amlodipine maleate as Mylan's product is AB-rated and can fully replace Pfizer's Norvasc unlike DRL's product.

Also, after the end of the generic exclusivity of Mylan, a large number of generic companies would enter the market causing a large price erosion and significantly impinge of the upsides for DRL, the international analyst said.

Hence while DRL has cleared a major bottleneck, legal barriers are yet to be cleared, the international analyst adds. This is important as Norvasc is the second biggest product for Pfizer, the most aggressive pharma company globally.