Hikma Pharmaceuticals (HKMPY) could get hit with sizeable downgrades Friday when it updates the market with new guidance in the wake of the Food & Drug Administration's rejection of its generic Advair Diskus product.

The company had guided for around 15% revenue growth in 2017, driven primarily by the expectation that its Advair application would be successful, enabling it to launch the product in the second half. But the FDA issued a complete response letter, classified as major, last week.

"We could receive further details at the 1Q IMS on May 19, but we expect a sizeable consensus downgrade with any updated guidance," said James Vane-Tempest at Jefferies.

Vane-Tempest also warned that the market might take time to realize just how important the release of generic Advair is to progress at Hikma, which could mean that downgrades become a recurring theme for the generic drug maker throughout the rest of the year.

He double-downgraded Hikma stock Wednesday, cutting its rating from buy to underperform, and slashing his price target by more than 30% to 1,450 pence.

Hikma shares fell by around 2.5% during early trading in London Wednesday, to change hands at an intraday low of 1,699 pence, which pushed its year to date loss to 7.41%. The Stoxx Europe 600 TMI Pharmaceuticals index was down 0.15% in morning trading. 

Advair is a blockbuster asthma treatment pioneered by Glaxo (GSK - Get Report) although it lost the patent in 2010 and has since been bracing for a flood of generics to hit the market. 

Hikma has stopped short of saying that it will not be able to launch Advair this year however, Barclays analysts have said that the chances of its being released in 2017 are near to zero. Vane-Tempest has said that Hikma's Advair is unlikely to appear in pharmacies before the second half of 2018.

With the market having priced in a 2017 launch for Advair a long time ago, along with solid takeup, it isn't difficult to comprehend the moving parts behind this week's likely downgrades.

However, a possible year or more delay to the release of Hikma's Advair could do more than just hit earnings estimates in 2017 and 2018.

It could render the entire product redundant for Hikma, or seriously damage its value to the company, given that other drugmakers now have a window to develop and launch their own products.

Mylan had its generic Advair knocked back in March, two months ahead of Hikma, although also with a major complete response letter.

Hikma will issue its firts-quarter interim management statement before the market opens on Friday.