Annual report pursuant to Section 13 and 15(d)

7. Accrued Expenses (Details)

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7. Accrued Expenses (Details) (USD $)
Dec. 31, 2014
Dec. 31, 2013
Payables and Accruals [Abstract]    
Accrued professional fees $ 574,186us-gaap_AccruedProfessionalFeesCurrent $ 1,106,358us-gaap_AccruedProfessionalFeesCurrent
Accrued research costs 573,879xbio_AccruedResearchCosts 29,682xbio_AccruedResearchCosts
Accrued payroll and benefits 67,120us-gaap_EmployeeRelatedLiabilitiesCurrent 99,548us-gaap_EmployeeRelatedLiabilitiesCurrent
Accrued bonus compensation 0us-gaap_AccruedBonusesCurrent 422,226us-gaap_AccruedBonusesCurrent
Other 194,506us-gaap_OtherAccruedLiabilitiesCurrent 169,053us-gaap_OtherAccruedLiabilitiesCurrent
Total $ 1,409,691us-gaap_AccruedLiabilitiesCurrent $ 1,826,867us-gaap_AccruedLiabilitiesCurrent