The company could soon be swallowed by a very large peer -- which also happens to be a business partner.Clinical-stage biotech Protagonist Therapeutics (PTGX 29.77%) was all the rage on the stock market Friday. The company's share price closed a dizzying 29.8% higher on the day, thanks to intense takeover speculation. That leap was particularly notable considering it was quite a downbeat day for stocks overall, with the S&P 500 (^GSPC -2.71%) sliding by almost 3%.Sale in the works?That speculation was fired ...