Maybe they feel that $60 million more now will result in significant growth which will allow for a higher sale price later. Diluting 12% during a period of rapid growth may be a smarter move than selling the company too cheaply now.
Maybe the $60 million will fund studies for a more rapid development of a treatment for nerve gas exposure.
Maybe another medication? Who knows? (I too wish they were more transparent).
I agree that it would be best to fund all the growth from revenues but this may not be possible if they need money quickly for specific needs.
Some entity (do we ever find out who?) was willing to invest $60 million for a 4.5% yield and the potential to buy shares later at what they hope will look like a cheap price. I assume that such an investment would have been made only after significant due diligence, so they must be convinced that something good may result.
Don't be so sure that there was no buyout attempt. It is possible that PLX is not yet ready to sell itself. I know you want your money quickly from a merger or buyout, but patience and time may ultimately result in greater rewards.