Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of MannKind Corp. (NASDAQ:56400P706) fell by more than 14% on heavy volume this morning following a downgrade by Goldman Sachs. Specifically, Goldman's analyst Jay Olson cut the firm's price target in half to a mere $3 a share, or 52% lower than where shares finished trading yesterday. 

The downgrade reportedly stems from two core issues: prescriptions for MannKind's newly launched inhaled insulin product Afrezza are falling well below the expected pace, and pricing pressure from payers for diabetes products in general might lead to a marked price reduction -- perhaps as much as 40% from current levels.

In its research note, Goldman also lowered its long-term commercial outlook for Afrezza, projecting 2025 sales of $1 billion, down from its former estimate of $2 billion. 

So what: MannKind needs Afrezza to get off to a strong start because the market has placed a huge premium on its shares heading into and following the drug's approval. Prior to today's drop, for instance, the company's market cap stood at close to $2.7 billion. A slow launch and/or a price reduction by MannKind's marketing partner Sanofi could put significant downward pressure on this stock going forward. 

Now what: The good news is that Afrezza has only been on the market for roughly a month at this point, meaning that it's far too early to panic, especially if you're on an optimist. When MannKind reports its first-quarter earnings sometime in the middle of May, we should have almost a full-quarter of script and revenue data to consider -- giving us a much better feel for how the launch is going and whether any steep discounts might be coming down the pike.