Indole, indazole and benzimidazole arylamides as P2X3 and P2X2/3 antagonists

A compound of formula III:

• or a pharmaceutically acceptable salt thereof,
• wherein:
• R1 is:
• C1-6alkyl;
• or
• halo;
• R2 is:
• C3-6cycloalkyl;
• C1-6alkoxy-C1-6alkyl;
• hydroxy-C1-6alkyl;
• or
• heteroaryl-C1-6alkyl selected from:
• pyrazinyl-methyl;
• pyridazinyl-methyl;
• pyrimidinyl-methyl;
• 1-pyrazinyl-ethyl;
• 1-pyridazinyl-ethyl;
• and 1-pyrimidinyl-ethyl;
• wherein the pyrazinyl, pyridazinyl and pyrimidinyl portions thereof may be optionally substituted once with methyl;
• R3 is:
• C1-6alkyl;
• hydroxy-C1-6alkyl;
• C1-6alkoxy-C1-6alkyl;
• halo-C1-6alkyl;
• C3-6cycloalkyl;
• C3-6cycloalkyl-C1-6alkyl;
• phenyl optionally substituted with:
• halo, C1-6alkyl, C1-6alkoxy or halo-C1-6alkyl;
• or
• phenyl-C1-6alkyl wherein the phenyl portion thereof is optionally substituted with:
• halo, C1-6alkyl, C1-6alkoxy or halo-C1-6alkyl;
• and
• X is:
• N or CRa wherein Ra is hydrogen, C1-6alkyl or halo.