• Moncef Slaoui was fired as Galvani Bioelectronics board chairman over "substantiated" allegations of sexual harassment, pharmaceuticals giant GlaxoSmithKline said.
• Slaoui was chief scientist of the U.S. government's Covid vaccine development effort Operation Warp Speed during the administration of then-President Donald Trump.
• Galvani Bioelectronics is a medical research company focused on developing bioelectronic medicines for the treatment of chronic diseases.
• It was formed through a partnership by GSK and Verily Life Sciences, a subsidiary of Google parent Alphabet.

Moncef Slaoui, who was chief scientist for the U.S government's Covid vaccine development effort Operation Warp Speed during the Trump administration, was fired as Galvani Bioelectronics chairman over "substantiated" sexual harassment allegations by a woman, it was announced Wednesday.

Slaoui's dismissal by the board of GlaxoSmithKline — the majority shareholder in Galvani Bioelectronics —came a month after GSK received a letter "containing allegations of sexual harassment and inappropriate conduct towards an employee of GSK by Dr. Slaoui," GSK said in a statement.

That conduct "occurred several years ago when he was an employee of GSK," the statement said.

Slaoui, 61, had spent 30 years at GSK, overseeing vaccine development at that pharmaceutical giant.

"Upon receipt of the letter, the GSK Board immediately initiated an investigation with an experienced law firm to investigate the allegations," GSK said. A spokesman said the law firm was Morgan, Lewis & Bockius.

"The investigation of Dr. Slaoui's conduct substantiated the allegations and is ongoing," GSK said.

"Dr. Slaoui's behaviours are wholly unacceptable," GSK said.

The allegations against him were made by one woman, according to GSK, which said the company was not aware of any other similar claims against Slaoui related to his tenure there.

Slaoui later Wednesday issued a statement expressing "deep regret" as he acknowledged his termination.

"I have the utmost respect for my colleagues and feel terrible that my actions have put a former colleague in an uncomfortable situation," Slaoui said. "I would like to apologise unreservedly to the employee concerned and I am deeply sorry for any distress caused."

"I would also like to apologise to my wife and family for the pain this is causing.I will work hard to redeem myself with all those that this situation has impacted," he said.

Slaoui also said that he is "taking a leave of absence from my current professional responsibilities effective immediately, to focus on my family."

Galvani Bioelectronics is a medical research company focused on developing bioelectronic medicines for the treatment of chronic diseases. It was formed through a partnership by GSK and Verily Life Sciences, which previously was known as Google Life Sciences. Verily is a subsidiary of Google parent Alphabet.

On Thursday, Slaoui stepped down as chief scientific officer of Centessa Pharamaceuticals because of the harassment allegations, and resigned as chairman of the board of the vaccine company Vaxcyte.

Slaoui's firing by GSK came 10 months after then-President Donald Trump tapped him to oversee the U.S. effort to development vaccines to fight the coronavirus pandemic.

He is married to Kristen Slaoui, who previously served as vice president and head of business development at GSK.

GSK CEO Emma Walmsley revealed Slaoui's firing in a letter to employees.

"On a personal level, I am shocked and angry about all of this, but I'm resolute," Walmsley wrote.

"I want to be clear that sexual harassment is strictly prohibited and will not be tolerated."

She also wrote that GSK will remove Slaoui's name from its research and development center in Rockville, Maryland. It had been called The Slaoui Center for Vaccines Research.

Walmsley also said she chose to "write openly to everyone because these issues are profoundly important to me."

"Since February, the highest levels of our company have been working to understand and address what happened," the CEO wrote.

"Protecting the woman who came forward and her privacy has been a critical priority throughout this time. This will continue," Walmsley said. "I respect and admire her courage and strength. I've spent many nights lately putting myself in her shoes. More than anything, this simply should not have happened."

Walmsley asked GSK workers to notify the company "if you have anything you want to share regarding this situation, a situation you've been in personally, or one you've been aware of."

In its statement, GSK said that Slaoui's actions "represent an abuse of his leadership position, violate company policies, and are contrary to the strong values that define GSK's culture."

"The company expects everyone at GSK to behave in accordance with its values, especially its leaders where its standards are the highest. Sexual harassment and any abuse of leadership position are strictly prohibited and will not be tolerated."

Slaoui last month joined Centessa Pharmaceuticals as chief scientific officer and advisor.

In a statement Thursday, Centessa Pharmaceuticals CEO Dr. Saurabh Saha said, "The Centessa management team and board of directors were troubled to learn of yesterday's news regarding Dr. Slaoui."

"Centessa is absolutely committed to fostering a culture of respect that is free from harassment and discrimination of any kind and are steadfastly committed to maintaining a work environment that is reflective of our strong values as a company," Saha said.

Centessa was founded by the venture capital firm Medicxi. Slaoui has been a partner in Medicxi since 2017. CNBC has reached out to comment from the firm.

Slaoui also had been chairman of the board of directors Vaxcyte until the GSK claims came to light.

"Based on these allegations and in alignment with Vaxcyte's corporate values and policies, the Board has requested Dr. Slaoui's resignation," Vaxcyte said in a Securities and Exchange Commission filing. "Dr. Slaoui has agreed and has resigned from the Board effective immediately.

A GSK spokeswoman, when asked if the company would share details of its investigation of Slaoui with other firms that he is affiliated with, said, "We are not sharing anything beyond what we have said publicly at this time."

Slaoui also has been advising the European Union on its coronavirus vaccine rollout. A report last month said that the EU sought advice from Slaoui, and that he said he had spoken several times with European Commission President Ursula von der Leyen about vaccine strategies.

The EC told CNBC in an emailed statement: "Mr Slaoui has not acted and does not act as an advisor to the European Commission. Mr Slaoui has participated in a few calls with the Commission President to discuss aspects linked to the development and production of vaccines and how to address variants of concern."

"Mr Slaoui has always insisted himself on his independence from the European Commission," the EC said. "The Commission does not intend to engage Mr Slaoui as an advisor or use his services in any way other than exchanging views through ad-hoc calls."

Slaoui in January submitted his resignation as Operation Warp Speed chief advisor to the then-incoming administration of President Joe Biden.

He was criticized when he became the operation's chief role because of his ties to the pharmaceuticals industry.

At the time he was appointed, he was on the board of Moderna. Slaoui resigned from Moderna and sold his shares in the company, whose Covid vaccine was the second to receive emergency use authorization in the United States. He said he donated their increase in value during the several days he had held the stock while at Operation Warp Speed.

But he had refused to sell his GSK shares, calling them his retirement plan.

GSK said Wednesday that Christopher Corsico, senior vice president of development and a member of Galvani's board, was appointed as the new chairman of Galvani.

GSK also said that Amy Altshul, its senior vice president of legal, R&D and global commercial franchises, was appointed to the Galvani board.

- CNBC's Steve Kopack contributed to this report.