Moderna CEO Stéphane Bancel announced his plan to donate to charity all of the after-tax proceeds of the original stock options he received upon joining the biotechnology company in 2013.

The donation is expected to amount to about $355 million (assuming the stock is priced at around $140 per share), and after $280 million in tax payments.

Bancel, who received the original stock option grant (due to expire in August 2023) in 2013, said he has never exercised a single stock option since joining the company 11 years ago.

He added that he offloaded Moderna stock under 10b5-1 plans and gifted the shares to charity, all of which were purchased using his family’s savings before Moderna went public.

Bancel said the stock option “will expire and be worthless” if not exercised now and it presents an opportunity “to create a positive change in the world.”

In an effort to prevent a high number of shares from flooding the market at once and potentially affecting the company’s stock price, Bancel has set up a 10b5-1 plan through which he plans to exercise 40,000 shares on Wednesday and 40,000 on Thursday each week, starting May 25, until fully exercised.

Bancel in a blog post, said:

My family also has our investment entity OCHA LLC, which, under another 10b5-1 plan, sells 10,000 shares each Thursday. These proceeds are invested in private companies trying to have a positive impact on the world: healthcare companies and companies focused on addressing the adverse impact of climate change. The 10b5-1 plan for OCHA LLC is scheduled to run through the end of 2022.

Moderna shares are down nearly 1% in pre-open Tuesday.