Mallak joined MSD in 2002, became associate vice president and managing director for the GCC in 2021, and expanded his role to Libya and Egypt in April 2026. He spearheads efforts to introduce innovative medicines and vaccines across oncology, rare diseases, cardiovascular disease, and respiratory care, while strengthening vaccine access and supporting national immunization efforts, including the addition of RSV vaccines to National Immunization Programs. Mallak is also vice chairman of the Pharmaceutical Research and Manufacturers Association Gulf (PHRMAG).