Benzinga's Top #PreMarket Losers

Onconova Therapeutics

shares fell 41.20% to $8.15 in the pre-market trading after the company announced results from Phase 3 ONTIME Trial of Rigosertib in higher risk myelodysplastic syndromes. Piper Jaffray downgraded the stock from Overweight to Neutral and lowered the price target from $38.00 to $9.00. Conns

shares dropped 28.62% to $39.83 in pre-market trading after the company issued a weak Q4 profit forecast. Yandex NV

dipped 5.98% to $37.45 after reporting Q4 results. Facebook

dipped 2.59% to $66.30 in the pre-market session after the company announced its plans to buy popular messaging service WhatsApp for $16 billion in cash and stock.