While congressional debate over the repeal and replacement of the Affordable Care Act managed to draw much of the attention away from the biotech sector Friday morning, a few companies caught investors' eyes, including Immunomedics (IMMU) - Get Report

The cancer drug research company hit new highs on Thursday, closing at $6.63 per share, up 3.2% from market's open. The company continued its upward trend Friday ahead of the opening bell. Shares were up 4.8% ahead of market's open, hitting $6.95 apiece. 

Meanwhile, PTC Therapeutics (PTC) - Get Report , a microcap biotech with Duchenne Muscular Dystrophy drugs, was falling quickly ahead of market's open. Shares were down 4.8%, hitting $8.04 apiece after performing poorly on Thursday. Shares fell 2.2% during normal trading hours Thursday. Last week PTC paid $140 million in cash to acquire Marathon Pharmaceuticals' Emflaza, a DMD drug mired in a price-gouging controversy.

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Mylan (MYL) - Get Report shares were also falling Friday ahead of the opening bell. The EpiPen-maker saw shares fall 2.9% ahead of market's open, hitting $40.41 apiece. This was likely thanks to reports that the company is recalling 81,000 EpiPens in  Australia, New Zealand, Europe and Japan this past week. 

Finally, Rigel Pharmaceuticals (RIGL) - Get Report were trading at heaving volume ahead of market's open. Shares were up 1.6%, hitting $3.10 apiece after the company climbed 10% Thursday.