SOUTH SAN FRANCISCO ( TheStreet) -- Theravance ( THRX) shares slumped Monday after pneumonia-related deaths were reported in patients taking the company's experimental lung drug Relovair. GlaxoSmithKline ( GSK), Theravance's Relovair development partner, sad it plans to seek U.S. and European regulatory approvals in the middle of the year based on the just-completed phase III program in chronic obstructive pulmonary disease (COPD) and asthma. But questions about mixed results from these Relovair studies, safety concerns and perhaps a recognition that Theravance's chances of being acquired by Glaxo have now dimmed, all conspired to drop the value of Theravance shares by $6.72, or 33%, to $13.46 in early Monday trading. Glaxo has been working with Theravance to develop Relovair as a follow-on drug to Advair, which brings in about $8 billion in revenue for the Big Pharma giant. Relovair is important because Advair has been gradually losing market share to AstraZeneca's ( AZN) more convenient asthma and COPD medicine Symbicort. As reported Monday, Relovair beat Advair at all tested doses in one large phase III study of COPD patients. But in a second COPD phase III study, Relovair at its highest dose failed to beat Advair. Glaxo said it was investigating reports of "fatal pneumonia" in patients treated with Relovair, primarily at the highest dose tested. Likewise, a large phase III trial program in asthma didn't produce pristine results. A 12-week study of Relovair versus placebo failed to demonstrate a statistically significant difference in lung function. Likewise, a 24-week study of Relovair compared to another asthma medicine failed a predefined superiority test of lung function. "Having undertaken an initial assessment of these data we believe they support our plan to seek global approvals of this once-daily medicine for the treatment of patients with COPD and asthma," said Glaxo's Darrell Baker, in a statement. --Written by Adam Feuerstein in San Francisco. >To contact the writer of this article, click here: Adam Feuerstein. >To follow the writer on Twitter, go to http://twitter.com/adamfeuerstein. >To submit a news tip, send an email to: firstname.lastname@example.org. Follow TheStreet on Twitter and become a fan on Facebook.