SYD985 treatment of T-DM1 refractory cancer patients

1. A method of treating a trastuzumab emtansine refractory tumor, which comprises administering to a trastuzumab emtansine refractory HER2 IHC 3+ or HER2 IHC 2+/FISH positive cancer patient an effective amount of a compound of formula (I)

wherein 2.6-2.9 represent an average DAR for the compound.

2. The method according to claim 1 , wherein the average DAR for the compound is about 2.8.

3. The method according to claim 1 , wherein the patient is refractory to both trastuzumab and trastuzumab emtansine.

4. The method according to claim 1 , wherein the patient is refractory to all of trastuzumab, lapatinib and trastuzumab emtansine.

5. The method according to claim 1 , wherein the patient is a breast cancer patient.

6. The method according to claim 1 , wherein said compound is administered at a dose of from about 0.9 mg/kg to about 2.1 mg/kg of patient body weight by intravenous administration.

7. The method according to claim 6 , wherein the dose is about 0.9 mg/kg, about 1.2 mg/kg, about 1.5 mg/kg, about 1.8 mg/kg, or about 2.1 mg/kg of patient body weight.

8. The method according to claim 6 , wherein the average DAR for the compound is about 2.8.

9. The method according to claim 6 , wherein said dose is administered every 3 weeks.

10. The method according to claim 6 , wherein the patient is a breast cancer patient.

11. The method according to claim 6 , wherein said dose is about 1.2 to about 1.8 mg/kg of patient body weight.

12. The method according to claim 11 , wherein said dose is about 1.2 mg/kg of patient body weight.

13. The method according to claim 12 , wherein said dose is administered every 3 weeks.

14. The method according to claim 13 , wherein the patient is a breast cancer patient.