Polymorphic forms of ST-246 and methods of preparation

1. A method of treating Orthopoxvirus infections comprising administering to a subject in need thereof a therapeutically effective amount of a polymorph Form I of 4-trifluoromethyl-N-(3,3a,4,4a,5,5a,6,6a-octahydro-1,3-dioxo-4,6-ethenocycloprop[f]isoindol-2(1H)-benzamide (ST-246) which shows an X-ray powder diffraction pattern having characteristic peaks at a reflection angle 2θ of about 7.63, 10.04, 11.47, 14.73, 15.21, 15.47, 16.06, 16.67, 16.98, 18.93, 19.96, 20.52, 20.79, 22.80, 25.16, 26.53, 27.20, 27.60, 29.60, 30.23, 30.49, 30.68, 31.14, 33.65, 34.33, 35.29, 35.56, 36.30, 37.36, 38.42, 38.66 degrees.

2. The method of claim 1 , wherein the polymorph Form I is at least about 70% free of other forms.

3. The method of claim 1 , wherein the polymorph Form I is at least about 80% free of other forms.

4. The method of claim 1 , wherein the polymorph Form I is at least about 90% free of other forms.

5. The method of claim 1 , wherein the polymorph Form I is at least about 95% free of other forms.

6. The method of claim 1 , wherein the polymorph Form I is at least about 99% free of other forms.

7. The method of claim 1 , wherein the polymorph Form I is administered orally.

8. A method of treating eczema vaccinatum comprising administering to a patient in need thereof a therapeutically effective amount of a polymorph Form I of 4-trifluoromethyl-N-(3,3a,4,4a,5,5a,6,6a-octahydro-1,3-dioxo-4,6-ethenocycloprop[f]isoindol-2(1H)-benzamide (ST-246) which shows an X-ray powder diffraction pattern having characteristic peaks at a reflection angle 2θ of about 7.63, 10.04, 11.47, 14.73, 15.21, 15.47, 16.06, 16.67, 16.98, 18.93, 19.96, 20.52, 20.79, 22.80, 25.16, 26.53, 27.20, 27.60, 29.60, 30.23, 30.49, 30.68, 31.14, 33.65, 34.33, 35.29, 35.56, 36.30, 37.36, 38.42, 38.66 degrees.