Shares of AveXis Inc. (AVXS) were down 5.4% to $68.11 in premarket trading on Tuesday, June 20. The Chicago firm after the market close on Monday unveiled plans to offer up to $200 million of shares in an underwritten public offering.

AveXis plans to give the underwriters a 30-day option to buy up to an additional $30 million of shares at the public offering price, less the underwriting discounts and commissions.

Meanwhile, shares of Clovis Oncology Inc. (CLVS) - Get Clovis Oncology, Inc. Report were up 1.7% to $89.37. J.P. Morgan analyst Cory Kasimov on Monday upped his price target on the stock to $111 from $72 after Clovis announced positive Phase 3 ARIEL3 data. Kasimov, who has an overweight rating on the stock, wrote in a note that the topline data "represent more or less a best case scenario for CLVS."

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"With this pivotal event in the rear view mirror, we expect attention to shift to the presentation of full data (likely at ESMO in Sept) and the strategic value of the various PARP assets," he added.

Boulder, Colo.-based Clovis on Monday said a Phase 3 trial of rucaparib achieved its primary endpoint of improved progression-free survival in all three ovarian cancer patient populations that were studied.

In other Clovis news, the firm after the market close on Monday said it has commenced an underwritten public offering to raise approximately $250 million. The company plans to use the net proceeds for general corporate purposes. Clovis plans to give underwriters a 30-day option to buy up to an additional 15 percent of the number of shares sold on the same terms and conditions.

Among the other biotech stock movers was Epizyme Inc. (EPZM) - Get Epizyme, Inc. Report . Shares of the Cambridge, Mass.-based firm were up 6.1% to $14.

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