Salts and forms of a WEE1 inhibitor

(R)-2-allyl-1-(7-ethyl-7-hydroxy-6,7-dihydro-5H-cyclopenta[b]pyridin-2-yl)-6-((4-(4-methylpiperazin-1-yl)phenyl)amino)-1,2-dihydro-3H-pyrazolo [3,4-d]pyrimidin-3-one (Compound A):

• wherein Compound A is selected from the group consisting of adipate salt Form A of Compound A, freebase Form E of Compound A, freebase Form F of Compound A and freebase Form J of Compound A, wherein:
• the adipate salt form A is characterized by one or more peaks in an X-ray powder diffraction pattern, wherein the one or more peaks are selected from 15.40 degrees 2θ ±0.2 degrees 2θ, 16.58 degrees 2θ ±0.2 degrees 2θ, 22.12 degrees 2θ ±0.2 degrees 2θ and 22.88 degrees 2θ ±0.2 degrees 2θ;
• and
• the freebase Form E of Compound A is a hydrate and is characterized by one or more peaks in an X-ray powder diffraction pattern, wherein the one or more peaks are selected from 6.20 degrees 2θ ±0.2 degrees 2θ, 12.40 degrees 2θ ±0.2 degrees 2θ, 18.96 degrees 2θ ±0.2 degrees 2θ and 22.62 degrees 2θ ±0.2 degrees 2θ;
• the freebase Form F of Compound A is characterized by one or more peaks in an X-ray powder diffraction pattern, wherein the one or more peaks are selected from 5.14 degrees 2θ ±0.2 degrees 2θ, 6.24 degrees 2θ ±0.2 degrees 2θ, 10.19 degrees 2θ ±0.2 degrees 2θ and 12.40 degrees 2θ ±0.2 degrees 2θ;
• and
• the freebase Form J is an anhydrate and is characterized by one or more peaks in an X-ray powder diffraction pattern, wherein the one or more peaks are selected from 6.08 degrees 2θ ±0.2 degrees 2θ, 10.58 degrees 2θ ±0.2 degrees 2θ, 19.42 degrees 2θ ±0.2 degrees 2θ, 21.93 degrees 2θ ±0.2 degrees 2θ and 23.23 degrees 2θ ±0.2 degrees 2θ.