A crossover study to assess the effect of repeated doses of fostamatinib on the levels of oral contraceptive (Microgynon® 30) in the blood of healthy female subjects. The study will consist of a screening period of up to 35 days, followed by 2 treatment periods (28 days each) of an oral contraceptive (Microgynon® 30) in the absence and presence of fostamatinib. The study will also evaluate the safety and tolerability of fostamatinib in combination with an oral contraceptive

Inclusion Criteria:

• Female subjects of age 18 to 45 years, inclusive, who are healthy, non-pregnant, not planning pregnancy within the study period
• Willing to use a highly effective method of birth control, ie, double barrier method contraception (condom and diaphragm with spermicide) from the first day of Period 1 until 28 days after the last dose
• Body weight of at least 50 kg and body mass index (BMI) between 18 and 30 kg/m2 inclusive
• Two negative pregnancy tests at least 7 days apart

Exclusion Criteria:

• History of any clinically significant disease or disorder
• History or presence of Gastrointestinal, hepatic, or renal disease
• Any condition listed as a contraindication in the Microgynon® 30 labelling
• Absolute neutrophil count less than 2.5 x 109/L.