Public Offerings of Common Stock

On December 8, 2020, the Company completed a public offering in which 1,725,000 shares of its common stock, including the underwriters’ exercise in full of an option to purchase an additional 225,000 shares, were sold to the public at a price of $181.00 per share (the “December Stock Offering”). The net proceeds of the December Stock Offering, after deducting underwriting discounts and commissions and other estimated offering expenses payable by the Company, were approximately $297.8 million.

On July 19, 2019, the Company completed a public offering in which 1,587,000 shares of its common stock, including the underwriters’ exercise in full of an option to purchase an additional 207,000 shares, were sold to the public at a price of $87.00 per share (the “July Stock Offering”). The net proceeds of the Stock Offering, after deducting underwriting discounts and commissions and other estimated offering expenses payable by the Company, were approximately $131.1 million.

On May 3, 2019, the Company completed a public offering in which 3,144,531 shares of its common stock, including the underwriters’ full exercise of an option to purchase up to an additional 410,156 shares, were sold to the public at a price of $64.00 per share. The total proceeds received by the Company from this offering, net of underwriting discounts and commissions and other estimated offering expenses payable by the Company, totaled approximately $189.6 million.

Stock Option and Incentive Plans

At the Company’s 2018 Annual Meeting of Stockholders held on May 16, 2018, the Company’s shareholders approved the 2018 Stock Option and Incentive Plan (the “2018 Plan”). Under the 2018 Plan the number of shares of the Company’s common stock that are reserved and available for issuance shall be 2,778,000 plus the number of shares of common stock available for issuance under the Company’s Amended and Restated 2012 Stock Option and Incentive Plan (the “2012 Plan”). The shares of common stock underlying any awards under the 2018 Plan, 2012 Plan and the Second Amended and Restated 2001 Repligen Corporation Stock Plan (the “2001 Plan,” and together with the 2018 Plan and 2012 Plan, the “Plans”) that are forfeited, canceled or otherwise terminated (other than by exercise) shall be added back to the shares of stock available for issuance under the 2018 Plan. At December 31, 2020, 2,306,943 shares were available for future grants under the 2018 Plan.

Stock-Based Compensation

The Company recorded stock-based compensation expense of $17.0 million, $12.8 million and $10.2 million for the years ended December 31, 2020, 2019 and 2018, respectively, for share-based awards granted under the Plans. The following table presents stock-based compensation expense in the Company’s consolidated statements of comprehensive income:


	For the Years Ended December 31,
	2020		2019		2018
	(Amounts in thousands)
Cost of product revenue	$	1,929	$	1,368	$	1,019
Research and development		1,534		1,373		917
Selling, general and administrative		13,544		10,106		8,256

Total stock-based compensation	$	17,007	$	12,847	$	10,192

The 2018 Plan allows for the granting of incentive and nonqualified options to purchase shares of common stock, restricted stock and other equity awards. Except for the grant to the Company’s Chief Executive Officer (“CEO”) in 2018 mentioned below, employee grants under the Plans generally vest over a three- to five-year period, with

20%-33%

vesting on the first anniversary of the date of grant and the remainder vesting in equal yearly installments thereafter. Nonqualified options issued to

non-employee

directors and consultants under the Plans generally vest over one year. In the first quarter of 2018, to create a longer-term retention incentive, the Company’s Compensation Committee granted long-term incentive compensation awards to its CEO which consisted of both stock options and restricted stock units that are subject to time-based vesting over nine years. Options granted under the Plans have a maximum term of ten years from the date of grant and generally, the exercise price of the stock options equals the fair market value of the Company’s common stock on the date of grant. At December 31, 2020, options to purchase 696,711 shares and 665,540 stock units were outstanding under the Plans.

The Company uses the Black-Scholes option pricing model to calculate the fair value of stock option awards on the grant date, and the Company uses the value of the common stock as of the grant date to value RSUs. The Company measures stock-based compensation costs at the grant date based on the estimated fair value of the award. The Company recognizes expense on awards with service-based vesting over the employee’s requisite service period on a straight-line basis. The Company has issued performance stock units to certain employees which are tied to the achievement of certain Company financial goal metrics and the passage of time. Finally, during 2020, the Company implemented a program that issued performance stock units to certain employees set to vest upon the achievement of individual goals and the passage of time. The Company recognizes expense on performance-based awards over the vesting period based on the probability that the performance metrics will be achieved. The Company recognizes stock-based compensation expense for options that are ultimately expected to vest, and accordingly, such compensation expense has been adjusted for estimated forfeitures.

The fair value of share-based awards granted during the years ended December 31, 2020, 2019 and 2018 were calculated using the following estimated assumptions:


	For the Years Ended December 31,
	2020	2019	2018
Expected term (in years)	5.5-6.5	5.5-6.5	5.5-7.5
Expected volatility (range)	45.14 – 50.87%	45.14 – 50.87%	45.14 – 50.87%
Risk-free interest rate	0.34 – 1.15%	1.55 – 2.56%	2.63 – 2.96%
Expected dividend yield	0%	0%	0%

Information regarding option activity for the year ended December 31, 2020 under the Plans is summarized below:


	Shares			Weighted average exercise price		Weighted- Average Remaining Contractual Term (in Years)		Aggregate Intrinsic Value (in Thousands)
Options outstanding at December 31, 2019		957,559		$	30.81
Granted		79,698		$	115.81
Exercised		(340,546	)	$	23.95
Forfeited/expired/cancelled		—		$	—

Options outstanding at December 31, 2020		696,711		$	43.88		6.90	$	102,958

Options exercisable at December 31, 2020		311,988		$	31.75		5.91	$	49,879

Vested and expected to vest at December 31, 2020 (1)		667,220					6.86	$	99,096

(1)

Represents the number of vested options as of December 31, 2020 plus the number of unvested options expected to vest as of December 31, 2020 based on the unvested outstanding options at December 31, 2020 adjusted for estimated forfeiture rates of 8% for awards granted to

non-executive

level employees and 3% for awards granted to executive level employees.

The aggregate intrinsic value in the table above represents the total

pre-tax

intrinsic value (the difference between the closing price of the common stock on December 31, 2020, the last business day of 2020, of $191.63 per share and the exercise price of each

in-the-money

option) that would have been received by the option holders had all option holders exercised their options on December 31, 2020. The aggregate intrinsic value of stock options exercised during the years ended December 31, 2020, 2019 and 2018 was $36.6 million, $5.5 million and $5.3 million, respectively.

The weighted average grant date fair value of options granted during the years ended December 31, 2020, 2019 and 2018 was $53.06, $31.27 and $18.90, respectively. The total fair value of stock options that vested during the years ended December 31, 2020, 2019 and 2018 was $2.8 million, $3.1 million and $2.3 million, respectively.

The fair value of stock units is calculated using the closing price of the Company’s common stock on the date of grant. Information regarding stock unit activity, which includes activity for restricted stock units and performance stock units, for the year ended December 31, 2020 under the Plans is summarized below:


	Shares			Weighted- Average Remaining Contractual Term (in Years)		Aggregate Intrinsic Value (in Thousands)
Unvested at December 31, 2019		734,984
Awarded		207,788
Vested		(244,648	)
Forfeited/expired/cancelled		(32,584	)

Unvested at December 31, 2020		665,540			3.32	$	127,904

Vested and expected to vest at December 31, 2020 (1)		650,047			3.01	$	124,568

(1)

Represents the number of vested stock units as of December 31, 2020 plus the number of unvested stock units expected to vest as of December 31, 2020 based on the unvested outstanding stock units at December 31, 2020 adjusted for estimated forfeiture rates of 8% for awards granted to

non-executive

level employees and 3% for awards granted to executive level employees.

The aggregate intrinsic value in the table above represents the total

pre-tax

intrinsic value (equal to the closing price of the common stock on December 31, 2020, the last business day of 2020, of $191.63 per share, as stock units do not have an exercise price) that would have been received by the stock unit holders had all holders exercised on December 31, 2020. The aggregate intrinsic value of stock units vested during the years ended December 31, 2020, 2019 and 2018 was $28.3 million, $17.5 million and $6.2 million, respectively.

The weighted average grant date fair value of stock units granted during the years ended December 31, 2020, 2019 and 2018 was $109.69, $49.68 and $30.30, respectively. The total fair value of stock units that vested during the years ended December 31, 2020, 2019 and 2018 was $10.8 million, $8.5 million and $4.6 million, respectively.

As of December 31, 2020, there was $46.7 million of total unrecognized compensation cost related to unvested share-based awards. This cost is expected to be recognized over a weighted average remaining requisite service period of 3.55 years. The Company expects 1,853,028 unvested options and stock units to vest over the next five years.