This is a question I am working on and struggling with understanding.

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Gilead Sciences, Inc. is an American biopharmaceutical company headquartered in Foster City, California that research, develops and commercializes drugs. NA SDAQ 2019-08-01 / 2020-09-02 12000 12000 11000 1 1000 10000 10000 9000 9000 gramm 8000 8000 7000 7000 Aug 01 20 19 Sep 02 2019 Oct 01 2019 Nov 01 20 19 Dec 02 20 19 Jan 01 2020 Feb 03 Mar 02 2020 2020 Apr 01 2020 May 01 2020 Jun 01 2020 Jul 01 2020 Aug 03 2020 Sep 01 2020 gilead 2019-08-01 / 2020-09-02 80 80 75 ham 75 70 70 W 25 Ww Mamma 65 Aug 01 20 19 Sep 03 20 19 Oct 01 2019 Nov 01 2019 Dec 02 20 19 Jan 02 2020 Feb 03 Mar 02 2020 2020 Apr 01 2020 May 01 2020 Jun 01 2020 Jul 01 2020 Aug 03 Sep 01 2020 2020 Question: Gilead stock price shows that it's return went up by 30% around May 2020, and then plummeted back to the stable price level observed in 2019. What is Gilead? What they did and what happened around May 2020 to Gilead? What caused a dramatic up and down of Gilead stock price