The investment firm owned by Microsoft Inc. co-founder Paul Allen said Wednesday that it is planning on exercising an option to sell its shares in Dreamworks Animation SKG Inc. in a secondary public offering.

DW Investment II Inc., one of the original investors in Glendale-based Dreamworks, requested that the offering occur after the Nov. 3 release of “Flushed Away,” the film company’s next release. Analysts have the offering estimated around $300 million.

If successful, the sale would end the relationship between the DreamWorks and Allen, who would loose about $200 million form his original investment if estimates of the offering are correct.

Shares of Dreamworks were up 21 cents early Thursday to $23.94.