Goldman Sachs maintained its Sell rating on MannKind Corporation (NASDAQ: MNKD) as it believes the recent rally in shares is not related to fundamentals as news flow is negative since Sanofi SA (ADR) (NYSE: SNY) dropped out of the Afrezza partnership in January.

"Specifically, Afrezza is averaging 400 TRx's per week in Feb/Mar down from 500 in 4Q15. At this rate, Afrezza scripts are only ~20% of the level Exubera reached at the same point post launch," analyst Jay Olson wrote in a note.

"Recognizing that Sanofi invested in physician and consumer targeted promotional campaigns to educate and create awareness for Afrezza, we are concerned that Afrezza scripts may continue to decline in the absence of Sanofi's marketing muscle and substantial diabetes expertise. It is unclear to us how MNKD intends to finance the promotion of Afrezza which has so far been costly and unprofitable."

As of December 31, MannKind had about $60 million in cash and $30 million available to borrow from the Mann Group.

Olson said Sanofi reported total Afrezza end market sales of only $8 million in 2015 resulting in about $170 million net loss of which MannKind owes Sanofi about $60 million for their 35 percent share.

Shares of MannKind were down 0.29 percent at $1.73, while Olson has a price target of $0.25.