Modified forms of ambroxol for therapeutic use

A compound according to Formula I:

• wherein
• indicates that the associated R or X group can be attached to any available carbon atom on the phenyl ring,
• Ra is hydroxyl (OH),
• Rb is H,
• Rc and Rd are each independently selected from H or a C1-3 alkyl or Rc and Rd are each part of a 4, 5, 6 or 7 membered ring structure that connects Rc and Rd,
• each of R1 to R14 is independently selected from H and D,
• X1 and X2 are independently selected from F, Cl, Br, and I, with the proviso that X1 and X2 are not both Br;
• or a pharmaceutically acceptable salt, solvate or prodrug thereof.