NPS Pharmaceuticals’ orphan drug Gattex, for short bowl syndrome (SBS), posted its first full quarter of earnings last week and so far, so good. The drug beat Jefferies’s estimates of $3.4 million for the second quarter, posting sales of $4.8 million.

Jefferies analyst Eun Yang, in an investor note, wrote that an earlier full-year forecast of $25-$30 million now appears “conservative.” The analyst pegged total prescriptions for the drug at over500 for the end of 2013. As of August 2, Gattex had been prescribed 318 times.

SBS is a condition which results from partial or complete surgical removal of the small and/or large intestine. Gattex works by reducing a patient’s dependency on paraentreal/intravenous fluid dependency. It is currently set at $295,000 for one year of treatment.

NPS also expects Gattex to launch in the EU by 2014 and sees international markets as a greater source of revenue than US sales.

But not every orphan-drug launch is going as smoothly. In the second quarter, Protalix Biotherapeutics’ Elelyso, which was approved earlier this year after being co-developed with Pfizer for Gaucher’s disease, missed estimates of $2.2 million, landing at $1.4 million for the quarter. Elelyso was rejected by the EMA (European Medicines Association).

Yang, in a separate investor note, speculated that the reasons why Elelyso isn’t catching on have to do with “little conversion to Elelyso from the therapies that patients are familiar with,” and, “given the 2Q sales, we now view uptake will be slower than expected.”

Two older therapies in particular—Genzyme’s Cerezyme and Shire’s Vpriv—have dampened the drug’s launch. Cerezyme, approved in 1994, brought in $1.23 billion in 2008 sales before a viral contamination incident at a Genzyme plant caused sales to drop by a third the following year. Faced with shortages, FDA gave Shire’s Vpriv, an alternative Gaucher’s disease treatment, a priority review in 2009, and it was approved in 2010.  

Elelyso is priced at $150,000 for a year of therapy, while Cerezyme costs $200,000 and Vpriv comes in at $170,000.

For a guide to the nuances of launching a rare-disorder product, see MM&M’s e-book, “Orphan-Drug Marketing,” free to download.