QuickLinks -- Click here to rapidly navigate through this document

EXHIBIT 21

SUBSIDIARIES OF VERTEX PHARMACEUTICALS INCORPORATED

Vertex Pharmaceuticals (San Diego) LLC, a Delaware limited liability company

VSD Sub I LLC, a Delaware limited liability company⁽¹⁾

VSD Sub II LLC, a Delaware limited liability company⁽²⁾

Vertex Holdings, Inc., a Delaware corporation

Vertex Securities Trust, a Massachusetts business trust⁽³⁾

Vertex Pharmaceuticals (Europe) Ltd., a United Kingdom limited liability company⁽⁴⁾

(1)

a subsidiary of Vertex Pharmaceuticals (San Diego) LLC

(2)

a subsidiary of VSD Sub I LLC

(3)

a subsidiary of Vertex Holdings, Inc.

(4)

jointly held by Vertex Securities Trust and Vertex Holdings, Inc.

QuickLinks

EXHIBIT 21

SUBSIDIARIES OF VERTEX PHARMACEUTICALS INCORPORATED