4. Property, Plant and Equipment, Net

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

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Manufacturing Facility

The Company owns a 135,000 square foot manufacturing facility located in Smithfield, Rhode Island. The facility was purchased in July 2018 for $8.0 million. During the remainder of 2018 and throughout 2019, it was renovated and customized to manufacture clinical supply of the Company’s product candidates and was placed into service in January 2020 after achieving the regulatory qualifications required to bring it to its intended use. The carrying value of the land represents an allocation of the original purchase price based on the value of comparable assets. The carrying value of the manufacturing facility represents the remaining purchase price, plus the capitalized design, demolition, construction and interest costs related to renovations and improvements. The Company continues to incur capital asset expenditures related to the operation of the manufacturing facility, which are capitalized as construction-in-progress until they are ready for their intended use and placed into service.

Depreciation and amortization expense was $7.7 million, $5.7 million and $3.0 million for the years ended December 31, 2021, 2020 and 2019, respectively.