Fourth Quarter 2021 Results
“Certara is entering 2022 well capitalized and positioned to continue executing on our long-term growth priorities. We are focused on investing in our business to drive mid-teens revenue growth, which we achieved in 2021 excluding Pinnacle 21.” said Andrew Schemick, chief financial officer.
Total revenue for the fourth quarter of 2021 was $75.3 million, representing growth of 17% over the fourth quarter of 2020. The increase in revenue was primarily due to $6.1 million in revenue from Pinnacle 21, which was acquired in the fourth quarter of 2021, and $4.6 million in growth from our software licenses and subscriptions and technology driven services.
Total cost of revenue for the fourth quarter of 2021 was $29.3 million, a decrease from $34.9 million in the fourth quarter of 2020, primarily due to a $7.2 million decrease in stock-based compensation cost, partially offset by a $1.2 million increase in software amortization expense and a $0.5 million increase in consulting cost. Excluding $0.8 million in incremental expense from Pinnacle 21, the cost of revenue decreased $6.4 million.
Total operating expenses for the fourth quarter of 2021 were $42.6 million, a decrease from $83.3 million in the fourth quarter of 2020, primarily due to a $46.4 million decrease in stock-based compensation expense, a $2.7 million increase in employee related costs, and a $1.4 million increase in acquisition costs. The remaining increases were primarily due to increases in insurance costs and intangible assets amortization expenses. Excluding $4.7 million in expense from Pinnacle 21, operating expenses decreased $45.4 million.
Net loss for the fourth quarter of 2021 was $9.7 million, compared to a net loss of $54.4 million in the fourth quarter of 2020. Excluding $0.4 million in net income from Pinnacle 21, the net loss was $10.1 million. The $44.7 million decrease in loss was primarily due to a $10.7 million increase in revenue, a $53.6 million decrease in stock-based compensation expense and a $2.2 million decrease in interest expense, partially offset by a $15.0 million increase in tax expense, a $2.3 million increase in other employee-related cost resulting from head count growth, a $2.0 million increase in intangible amortization expense, and a $1.4 million increase in acquisition cost.
Diluted loss per share for the fourth quarter 2021 was ($0.06), as compared to ($0.40) in the fourth quarter of 2020.
Adjusted EBITDA for the fourth quarter of 2021 was $28.2 million compared to $22.2 million for the fourth quarter of 2020, representing 27% growth. See note (1) in the section A Note on Non-GAAP Financial Measures below for more information on adjusted EBITDA.
Adjusted net income for the fourth quarter of 2021 was $1.4 million compared to $10.3 million for the fourth quarter of 2020. Adjusted diluted earnings per share for the fourth quarter 2021 was $0.01 compared to $0.07 for the fourth quarter of