4. Property, Plant and Equipment, Net

Property, plant and equipment, net consisted of the following (in thousands):

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Manufacturing Facility

On July 31, 2018, the Company completed its purchase of a 135,000 square foot manufacturing facility located in Smithfield, Rhode Island for a purchase price of $8.0 million. In August 2018, the Company began renovations to customize this facility to manufacture clinical supply of its product candidates. Of the total purchase price, $1.3 million was allocated to the value of land acquired based on the value of comparable assets, and $6.7 million was allocated to construction in progress, as the building was not ready for its intended use. During the years ended December 31, 2019 and 2018, the Company capitalized, as construction-in-progress, the design, demolition, construction and interest costs related to the renovation project, as well as costs for manufacturing equipment to be used in the facility. In January 2020, after achieving the regulatory qualifications required to bring it to its intended use, the Company placed the manufacturing facility and manufacturing equipment into service. In connection with placing the manufacturing facility into service, $30.5 million and $7.8 million of construction-in-progress was transferred to depreciating asset accounts classified as manufacturing facility and manufacturing equipment, respectively. The Company continues to incur capital asset expenditures related to the operation of the manufacturing facility.

Depreciation and amortization expense was $5.7 million, $3.0 million and $1.3 million for the years ended December 31, 2020, 2019 and 2018, respectively.

5. Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following (in thousands):