Redmile Group Reports 9.9% Stake in Atara Biotherapeutics via Warrant Adjustments

Redmile Group, LLC, along with Jeremy C. Green and affiliated entities, filed an Amendment No. 2 to Schedule 13D for Atara Biotherapeutics, Inc. (ATRA) on May 14, 2026. The reporting persons collectively hold 950,994 shares of Common Stock, representing a 9.9% ownership stake. This position consists of 441,701 shares held directly by various Redmile Funds and 509,293 shares issuable upon the exercise of pre-funded warrants. The filing clarifies that the reporting persons have not engaged in any new market transactions since their previous filing. Instead, the reported increase in beneficial ownership is due solely to an increase in the issuer's aggregate outstanding Common Stock, which consequently adjusted the number of shares issuable under a 9.99% Beneficial Ownership Limitation. Redmile Biopharma Investments II, L.P. and Redmile Strategic Long Only Trading Sub, Ltd. are among the key entities within the reporting group. Jeremy C. Green, as the principal of Redmile Group, LLC, may be deemed to share voting and dispositive power over these securities.