Looks like Hurvitz aquired ~4.5M shares under their options program at 0.001/shr (must be nice) then sold ~1.5M shares to cover the taxes. This is normal and smart. Taxes must be paid based on the value of the option purchased vs the stock price on the day that the option was exercised. If the stock went down, he would still be owing the taxes. People have learned from the dot com era that no matter what you think a stock might do, taxes must be paid. Cover the nut then speculate.
Hurvitz now holds 455,240 shares of plx down from 6,270,949 which was reported in the plx annual report. Could he be selling in preparation for Teva to be able to make an offer? It would seem improper for Teva to be permitted to make an offer to buy a company that would personally benefit Hurvitz with such a windfall.
It would be highly unethical and, indeed, illegal for a man with insder information --- being the chairman of the board of a publicly traded company like PLX --- to sell almost all of his shares, in the millions, knowing that something materially negative was coming down....
(Of course, business people do both unethical and illegal thing all the time, when it comes to money; but let's hope that this was/is not one of such a case, being that Eli Hurvitz is such an important, public man, chairman of the board for both small Protalix and giant TEVA, having carefully guided and shaped both companies for so many years...)
Therefore, the central "theory" that Eli Hurvitz is selling so he would not be seen as personally benefiting from such a large windfall, when/if giant TEVA bought small Protalix DOES SEEM to be a highly attractive one.