NEW YORK ( TheStreet) -- Keryx Pharmaceuticals ( KERX) lost its largest shareholder. Mutual fund giant Fidelity Management and Research reduced its ownership position in Keryx from 5.8 million shares to 875,000 shares, according to a regulatory filing Tuesday. No reason was given for Fidelity's decision to significantly lighten its Keryx ownership stake from what was a market-leading 8% down to 1.25%. Speculation that Fidelity was dumping Keryx shares was the subject of Wall Street trading chatter in early September. Keryx expects to announce top-line results from a phase III study of its colon cancer drug perifosine early next year. Perifosine development and marketing rights are co-owned by Canadian drug maker Aeterna Zentaris ( AEZS). Fidelity's selling likely helps explain why Keryx shares are down about 22% since early September, significantly under-performing the broader biotech sector. In Tuesday trading, Keryx was down 2% to $3.12. Keryx's new, top shareholder is Balyasny Asset Management, which owns 3.3 million shares, or 4.76%, as of June 30, according to regulatory filings. --Written by Adam Feuerstein in Boston. >To contact the writer of this article, click here: Adam Feuerstein. >To follow the writer on Twitter, go to http://twitter.com/adamfeuerstein. >To submit a news tip, send an email to: email@example.com. Follow TheStreet on Twitter and become a fan on Facebook.