Our share-based compensation expense is associated with RSUs, PSUs, and our Employee Stock Purchase Plan, or ESPP. The following table summarizes our share-based compensation expense included in our consolidated statements of operations for the periods shown:


	Three Months Ended June 30,				Six Months Ended June 30,
(In millions)	2024		2023		2024		2023
Cost of sales	$	4.1	$	3.9	$	7.8	$	7.2
Research and development	13.9		11.8		25.4		22.9
Selling, general and administrative	26.7		24.0		50.5		44.8
Total share-based compensation expense	$	44.7	$	39.7	$	83.7	$	74.9

As of June 30, 2024, unrecognized estimated compensation costs related to RSUs and PSUs totaled $306.9 million and are expected to be recognized over a weighted-average period of approximately 2.0 years.

In the first quarter of 2024, we issued 7.9 million treasury shares to settle a portion of the 2023 Warrants. In the second quarter of 2024, we issued 4.6 million treasury shares to settle the remaining portion of the 2023 Warrants. See Note 5 “Debt—Senior Convertible Notes” to the consolidated financial statements for more information.

In the first quarter of 2024, we issued 1.5 million treasury shares in connection with our achievement of the second sales-based milestone under the Restated Collaboration Agreement. See Note 2 “Development and Other Agreements—Collaboration with Verily Life Sciences” to the consolidated financial statements for more information.

Repurchased shares of our common stock are held as treasury shares until they are reissued or retired. We have not yet determined the ultimate disposition of repurchased shares and consequently we continue to hold them as treasury shares rather than retiring them. Authorization of future stock repurchase programs is subject to the final determination of our Board of Directors.