The US Food and Drug Administration (FDA) gave a green signal to Alexion Pharmaceutical Inc's drug on Tuesday to treat rare and fatal genetic disorder. On the same day, shares of the company were up 4.5% at $187.22.

Kanuma, enzyme-replacement therapy of Cheshire headquartered Alexion, received approval of European Union in September this year to treat people with acid lipase deficiency (LAL-D), a medical condition that could result into heart disease, liver failure and even early death.

According to Alexion, the US has a few thousand individuals with LAL-D. Every year, approximately four to eight infants take birth with infantile form of LAL-D, it added. As the new therapy is capable of treating ultra-rare and potentially fatal genetic disorder, chances are high that its price will be extremely high.

Alexion hopes the drug, Kanuma, will help the company to generate annual sales in excess of $1 billion. David Hallal, Chief Executive of Alexion, said during a telephone interview, “But given the extremely low awareness of this disease, the high mortality and low incidence in prevalence, we would expect the dynamics of this launch to be slow and steady. It takes many years in ultra-rare diseases to reach a $1 billion threshold”.

As per medical experts, people start experiencing onset of LAL-D when they are around the age of five. Most infants who take birth with the disease die within one year. In a recent trial, six of nine babies who were given Kanuma survived beyond one year.