The number of shares, terms, and vesting periods are determined by the Company’s Board of Directors or a committee thereof on an award-by-award basis. RSUs granted to employees generally vest ratably over four years from the month of the anniversary date in which the RSUs are granted. Options and RSUs granted to our non-employee directors vest in full upon completion of one year of service on the anniversary following the date of the grant. Options generally vest ratably over service periods of four years. Options granted after December 5, 2012 expire eight years from the date of grant, and options granted prior to that date generally expire ten years from the date of grant. In September 2014, the Company began generally issuing RSUs in lieu of stock options.

The number of RSUs awarded to certain executive officers that ultimately vest may be increased or reduced based on certain additional performance and market conditions. The performance and market conditions associated with awards granted during the transition period ended December 31, 2020 include vesting that is based 50% on achieving certain levels of earnings per share targets, and 50% based on achieving certain performance targets compared to the performance of the Nasdaq Healthcare Provider Index. The Company estimates the likelihood of achievement of performance conditions at the end of each period.

During the transition period ended December 31, 2020, the Company granted stock-based awards to the Company's President and Chief Executive Officer as an inducement material to his commencement of employment and entry into an employment agreement with the Company. The awards that were granted consist of time-based RSUs as well as RSUs that have the same performance conditions as other executives discussed in the preceding paragraph. The awards also consist of time-based stock options as well as stock options with market-based vesting conditions based on achievement of certain levels of Myriad's stock price for a period of 20 consecutive days. The inducement awards were made in accordance with Nasdaq Stock Market rules and were not made under the Company's existing equity plans. The inducement awards are included in the tables presented.

A summary of option activity under the Company's equity plans, including the Company's inducement awards, is as follows for the transition period ended December 31, 2020:


(number of shares in millions)	Number of shares	Weighted average exercise price
Options outstanding at beginning of period	4.8	$	24.47
Options granted	0.7	13.38
Less:
Options exercised	—	—
Options canceled or expired	(0.3)	19.12
Options outstanding at end of period	5.2	23.24
Options exercisable at end of period	4.6	24.71
Options vested and expected to vest	5.2	23.24

The fair value of options granted is estimated on the grant date using the Black-Scholes option-pricing model except for options with a market condition, which are valued using a Monte Carlo Simulation. The fair value of the stock options is amortized on a straight-line basis over the requisite service period of the awards, which is generally the vesting period. During the transition period ended December 31, 2020, the valuation assumptions used for stock options were as follows:


			Transition Period Ended December 31,
			2020
Risk-free interest rate			0.3% - 0.5%
Expected dividend yield			—%
Expected life (in years)			4.75
Derived service period (in years)			1 - 2.6
Expected volatility			73% - 77%


	Options outstanding and exercisable
Range of exercise prices	Number outstanding at December 31, 2020	Weighted average remaining contractual life (years)	Weighted average exercise price
13.38 - 19.47	1.7	2.92	$	19.13
21.29 - 25.39	0.5	0.98	23.97
26.49 - 26.49	1.5	0.70	26.49
27.07 - 36.55	1.5	1.69	27.18
	5.2	1.75	$	24.71

As of December 31, 2020 there was $4.6 million of unrecognized share-based compensation expense related to the inducement stock options that will be recognized over a weighted-average period of 2.5 years.

A summary of the RSU activity under the Company's equity plans, including the Company's inducement awards and RSU awards with performance metrics, is as follows for the transition period ended December 31, 2020:


	2020
(number of shares in millions)	Number of shares	Weighted average grant date fair value
RSUs outstanding at beginning of period	2.3	$	32.50
RSUs granted	2.1	13.69
Less:
RSUs vested	(0.9)	32.22
RSUs canceled	(0.3)	31.51
RSUs outstanding at end of period	3.2	$	20.56

The weighted average grant-date fair value of restricted stock units grants during the transition period ended December 31, 2020, and the fiscal years ended June 30, 2020, June 30, 2019, and June 30, 2018 was $13.69, $27.96, $46.62 and $32.67, respectively.

The fair value of restricted stock units that vested during the transition period ended December 31, 2020, and the fiscal years ended June 30, 2020, June 30, 2019, and June 30, 2018 was $29.1 million, $32.4 million, $27.6 million and $20.4 million, respectively.

As of December 31, 2020, there was $54.3 million of total unrecognized share-based compensation expense related to RSUs that will be recognized over a weighted-average period of 2.7 years. We expect all unvested awards to vest and recognize forfeitures as they occur.


	Transition Period Ended December 31,		Years Ended June 30,
(in millions)	2020		2020		2019		2018
Cost of molecular diagnostic testing	$	0.6	$	1.2	$	0.8	$	0.7
Cost of pharmaceutical and clinical services	0.1		0.3		0.2		0.2
Research and development expense	2.4		5.0		5.4		4.3
Selling, general, and administrative expense	11.8		18.7		27.1		21.9
Total share-based compensation expense	$	14.9	$	25.2	$	33.5	$	27.1

The Company has unrecognized share-based compensation cost related to share-based compensation granted under its current plans. The estimated unrecognized share-based compensation cost and related weighted average recognition period, aggregate intrinsic value of options outstanding, aggregate intrinsic value of options that are fully vested and aggregate intrinsic value of RSUs vested and expected to vest is as follows:


(in millions)	As of December 31, 2020
Unrecognized share-based compensation cost	$	54.3
Aggregate intrinsic value of options outstanding	5.0
Aggregate intrinsic value of options fully vested	0.7
Aggregate intrinsic value of RSUs outstanding	63.1

On December 5, 2012, following stockholder approval, the Company adopted the 2012 Employee Stock Purchase Plan (the “2012 Purchase Plan”), under which 2.0 million shares of common stock have been authorized. Shares are issued under the 2012 Purchase Plan twice yearly at the end of each offering period. At December 31, 2020, a total of 1.8 million shares of common stock had been purchased under the 2012 Plan. Shares purchased under and compensation expense associated with the 2012 Plan for the years reported are as follows:


	Transition Period Ended December 31,		Years Ended June 30,
(in millions)	2020		2020		2019		2018
Shares purchased under the plans	0.1		0.3		0.2		0.1
Plan compensation expense	$	0.6	$	1.7	$	1.0	$	0.1

From June 1, 2017 through May 31, 2018 there was an amendment to the 2012 Purchase Plan implemented such that the plan was non-compensatory. As of December 31, 2020, there is $0.5 million unrecognized share-based compensation expense related to the 2012 Purchase Plan.

The fair value of shares issued under the Plan that was in effect for each period reported was calculated using the Black‑Scholes option-pricing model using the following weighted-average assumptions:


	Transition Period Ended December 31,	Years Ended June 30,
	2020	2020	2019	2018
Risk-free interest rate	0.2%	1.8%	2.1%	2.1%
Expected dividend yield	—%	—%	—%	—%
Expected life (in years)	0.5	0.5	0.5	0.5
Expected volatility	94%	99%	55%	45%