Oral solution formulation

1. An oral aqueous solution comprising 6-acetyl-8-cyclopentyl-5-methyl-2-(5-piperazin-1-yl-pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one (palbociclib), or a lactate or malate salt thereof, and a buffer system comprising lactic acid or malic acid, wherein the palbociclib, or a lactate or malate salt thereof, is at a solution concentration of up to about 40.0 mq/mL.

2. The oral aqueous solution of claim 1 , comprising palbociclib, or a lactate salt thereof, at a solution concentration of about mg/mL.

3. The oral aqueous solution of claim 1 , wherein the buffer system comprises DL-lactic acid, D-lactic acid or L-lactic acid at a solution concentration of up to about 0.2M.

4. The oral aqueous solution of claim 3 , wherein the buffer system comprises DL-lactic acid at a solution concentration of about 0.1M.

5. The oral aqueous solution of claim 1 , comprising palbociclib, or a malate salt thereof, at a solution concentration of up to about 15.0 mg/mL.

6. The oral aqueous solution of claim 5 , comprising palbociclib, or a malate salt thereof, at a solution concentration of about 12.5 mg/mL or about 10.0 mg/mL.

7. The oral aqueous solution of claim 5 , wherein the buffer system comprises DL-malic acid, D-malic acid or L-malic acid at a solution concentration of about 0.2M.

8. The oral aqueous solution of claim 1 , having a pH from about 3.6 to about 4.0.

9. The oral aqueous solution of claim 1 , further comprising one or more pharmaceutically acceptable sweeteners selected from xylitol at a solution concentration from about 100.0 mg/mL to about 350.0 mg/mL and sucralose at a solution concentration from about 1.0 mg/mL to about 10.0 mg/mL, or mixtures thereof.

10. The oral aqueous solution of claim 1 , wherein the solution further comprises one or more pharmaceutically acceptable flavorants.

11. The oral aqueous solution of claim 1 , further comprising one or more pharmaceutically acceptable excipients selected from the group consisting of preservatives, antioxidants, pH adjusting agents, diluents, solubilizing agents, viscosity modifying agents and colorants.

12. The oral aqueous solution of claim 11 , wherein the solution comprises one or more preservatives selected from benzoic acid and sodium benzoate, each at a solution concentration from about 1.0 mg/mL to about 1.5 mg/mL.

13. The oral aqueous solution of claim 11 , wherein the solution comprises one or more antioxidants selected from propyl gallate and disodium EDTA, each at a solution concentration from about 0.1 mg/mL to about 1.0 mg/mL.

14. An oral aqueous solution comprising palbociclib at a solution concentration of about 25.0 mg/mL, lactic acid at a solution concentration of about 0.1M, xylitol at a solution concentration of about 320.0 mg/mL and sucralose at a solution concentration of about 8.0 mg/mL, said solution having a pH of from about 3.6 to about 4.0.

15. An oral aqueous solution comprising palbociclib at a solution concentration of about 12.5 mg/mL or about 10.0 mg/mL, malic acid at a solution concentration of about 0.2M, xylitol at a solution concentration of about 100.0 mg/mL and sucralose at a solution concentration of about 1.0 mg/mL, said solution having a pH of from about 3.6 to about 4.0.

16. The oral aqueous solution of claim 14 , further comprising: (a) a pharmaceutically acceptable flavorant at a solution concentration from about 1.0 mg/mL to about 3.0 mg/mL; (b) sodium benzoate at a solution concentration of about 1.0 mg/mL to about 1.5 mg/mL; and/or (c) propyl gallate at a solution concentration of about 0.10 mg/mL to about 1.0 mg/mL.

17. The oral aqueous solution of claim 14 , further comprising: (a) a pharmaceutically acceptable flavorant at a solution concentration of about 3.0 mg/mL; (b) sodium benzoate at a solution concentration of about 1.0 mg/mL; and (c) propyl gallate at a solution concentration of about 0.10 mg/mL.

18. The oral aqueous solution of claim 15 , further comprising: (a) a pharmaceutically acceptable flavorant at a solution concentration from about 1.0 mg/mL to about 3.0 mg/mL; (b) sodium benzoate at a solution concentration of about 1.0 mg/mL to about 1.5 mg/mL; and/or (c) propyl gallate at a solution concentration of about 0.10 mg/mL to about 1.0 mg/mL.