More than 100 scientists and researchers, including Joep Lange, former president of the International AIDS Society, or IAS, and a leading scientist on HIV research, were among the 298 passengers killed in the MH17 crash in Ukraine on Thursday.

The Australian reported that 108 conference participants, who were on their way to the 20thInternational AIDS Conference due to begin Sunday in Melbourne, lost their lives in the fatal Ukraine plane crash.

Michel Sidibe, Executive Director of UNAIDS, tweeted:

“The International AIDS Society today expresses its sincere sadness at receiving news that a number of colleagues and friends en route to attend the 20thInternational AIDS Conference taking place in Melbourne, Australia, were on board the Malaysian Airlines MH17 flight that has crashed over Ukraine earlier today,” the organization said, in a statement released Friday, adding that the HIV/AIDS movement "has truly lost a giant” with Lange's death.

While the identities of the victims have not been officially confirmed by the airline, Lange’s office in Amsterdam confirmed in a statement that he had died in the crash.

Expressing his condolences, Gregg Gonsalves, an American academic and AIDS activist, stated that Lange “was a leading AIDS researcher and clinician and an activist at heart.”

"Joep was a visionary amongst HIV researchers," American HIV researcher Rick Elion told Vox News. "He was acutely aware of the multiple dimensions of HIV spanning science to society and had a heart of gold."

Lange had been involved in HIV treatment and research since 1983, and was one of the key researchers behind several anti-retroviral therapy trials, chiefly involving the prevention of mother-to-child transmission of the virus.

Glenn Thomas, a media adviser to the Geneva-based World Health Organization, or WHO, is also believed to be among the dead.

Haileyesus Getahun, coordinator of the WHO’s Global TB program, tweeted: 

Saddened to learn that my friend and @WHO staff who was traveling to @AIDS_conference to Melbourne was on flight #MH17. RIP #Glenn Thomas