These studies compare monozygotic and dizygotic twins for medical, genetic, or psychological characteristics to try to isolate genetic influence from epigenetic and environmental influence. Twins that have been separated early in life and raised in separate households are especially sought-after for these studies, which have been used widely in the exploration of human nature. Classical twin studies are now being supplemented with molecular genetic studies which identify individual genes. Unusual twinnings
Bi-paternal twins
This phenomenon is known as heteropaternal superfecundation. One 1992 study estimates that the frequency of heteropaternal superfecundation among dizygotic twins, whose parents were involved in paternity suits, was approximately 2.4%; see the references section, below, for more details.Dizygotic twins from biracial couples can sometimes be mixed twins, which exhibit differing ethnic and racial features. One such pairing was born in London in 1993 to a white mother and Caribbean father. Monozygotic twins of different sexes
Among monozygotic twins, in extremely rare cases, twins have been born with different sexes (one male, one female). When monozygotic twins are born with different sexes it is because of chromosomal defects. The probability of this is so small that multiples having different sexes is universally accepted as a sound basis for in utero clinical determination that the multiples are not monozygotic. Another abnormality that can result in monozygotic twins of different sexes is if the egg is fertilized by a male sperm but during cell division only the X chromosome is duplicated. This results in one normal male (XY) and one female with Turner syndrome (45,X).
Bosutinib (rINN/USAN; codenamed SKI-606, marketed under the trade name Bosulif) is a small molecule BCR-ABL and src tyrosine kinase inhibitor used for the treatment of chronic myelogenous leukemia. Originally synthesized by Wyeth, it is being developed by Pfizer. Mechanism
It is an ATP-competitive Bcr-Abl tyrosine-kinase inhibitor with an additional inhibitory effect on Src family kinases (including Src, Lyn and Hck). It has also shown activity against the receptors for platelet derived growth factor and vascular endothelial growth factor. Bosutinib inhibited 16 of 18 imatinib-resistant forms of Bcr-Abl expressed in murine myeloid cell lines, but did not inhibit T315I and V299L mutant cells.Bosutinib is metabolized through CYP3A4. Medical uses
Bosutinib received US FDA and EU European Medicines Agency approval in September 2012, and March 2013, respectively for the treatment of adults with Philadelphia chromosome-positive (Ph+) chronic myelogenous leukemia (CML) with resistance, or intolerance to prior therapy. Contraindications
Bosutinib has two known absolute contraindications, which are: known hypersensitivity to bosutinib and liver impairment. Interactions
Bosutinib is both a substrate and an inhibitor of P-glycoprotein (P-gp) and CYP3A4. Hence P-gp and CYP3A4 inhibitors may increase plasma levels of bosutinib. Likewise CYP3A4 inducers may reduce plasma concentrations of bosutinib. It may also alter the metabolism and uptake (into the GIT by means of its P-gp inhibitory effects) of other drugs that are substrates for P-gp and CYP3A4. Notes
See also
Discovery and development of Bcr-Abl tyrosine kinase inhibitors

References
External links
"Bosutinib". Drug Information Portal. U.S. National Library of Medicine.