4. Property, Plant and Equipment, Net

During the three and six months ended June 30, 2026, total depreciation and amortization expense, including finance lease amortization (see Note 10), was $10.3 million and $20.2 million, respectively. During the three and six months ended June 30, 2025, total depreciation and amortization expense was $6.7 million and $12.8 million, respectively. Construction-in-progress as of June 30, 2026 primarily related to the design and construction of the Company’s new headquarters facility in Somerville, Massachusetts and manufacturing facilities in Italy. Construction-in-progress as of December 31, 2025 primarily related to the in-process construction of manufacturing equipment.

The Company capitalized costs associated with the development of internal-use software of $2.5 million and $4.4 million during the three and six months ended June 30, 2026, respectively, and $2.2 million and $4.0 million during the three and six months ended June 30, 2025, respectively. The Company recorded amortization expense of $0.8 million and $1.5 million during the three and six months ended June 30, 2026, respectively, and $0.4 million during each of the three and six months ended June 30, 2025. The net book value of internal-use software was $14.1 million and $11.2 million as of June 30, 2026 and December 31, 2025, respectively, of which $0.7 million and $0.1 million was included in construction-in-progress as of those respective dates.

Substantially all of the Company's tangible property, plant and equipment are held in the United States.