Receptos Inc (NASDAQ:RCPT), Enzon Pharmaceuticals Inc (NASDAQ:ENZN) and Applied Micro Circuits Corporation (NASDAQ:AMCC) are this Tuesday’s top gainers midday. The losers are Qiwi PLC (NASDAQ:QIWI), Tasman Metals Ltd (NYSEMKT:TAS) and Magnum Hunter Resources Corp (NYSE:MHR).

Receptos

Receptos soars on new drug announcement

Receptos Inc (NASDAQ:RCPT) soared +35.96% by midday this Tuesday after revealing that its experimental multiple sclerosis drug met its main goal in a mid-stage trial. Billionaire hedge fund manager Thomas Steyer holds 310,000 RCPT shares after significantly upping his stake in the first quarter of the year.

Enzon Pharmaceuticals Inc (NASDAQ:ENZN) jumped +18.21% and continues on what has been a solid month-long run, its price up +21.73% since May 12th. Carl Icahn has maintained a 5.9-million-share position in the biotech firm across several quarters.

The share price of Applied Micro Circuits Corporation (NASDAQ:AMCC) surged +10.24% midday after Canaccord initiated coverage of the chipmaker, assigning it a “buy” rating and a price target of $16. Julian Robertson initiated a position in AMCC in the fourth quarter of 2013 and scaled back his allocation in Q1.

QIWI, MHR Dip, but Future Looks Bright

Russian payment services provider Qiwi PLC (NASDAQ:QIWI) dipped -6.64%. The Tiger Global pick said today that it has filed a registration statement with the SEC for a proposed underwritten public offering of an aggregate of 7.9 million of its Class B shares. It also stands to benefit should Russia move to create a national credit-payment system. In other words, QIWI investors shouldn’t be very concerned about today’s midday price drop.

The share price of Tasman Metals Ltd (NYSEMKT:TAS) fell -6.37%. The junior resource company and long-time George Soros holding has taken a major hit since ending merger negotiations with Flinders Resources in May, its price falling -28.4% since then.

Last on today’s list of midday losers is Magnum Hunter Resources Corp (NYSE:MHR). Its share price dropped -5.88% today, even as the company announced a bid for Australian firm Ambassador Oil & Gas. Magnum Hunter has had a strong run in recent weeks, and its price has surged +12.72% over the past month. Investors, including George Soros, needn’t worry.