司美替尼(Selumetinib)是丝裂原活化蛋白激酶1和2(MEK1/2)的抑制剂，适用于治疗2岁及以上患有1型神经纤维瘤病（NF1）导致的有症状，无法手术的丛状神经纤维瘤（PN）的儿童患者。

 Selumetinib is an inhibitor of mitogen-activated protein kinases 1 and 2(MEK1/2) for the treatment of symptomatic, inoperable neurofibromatosis type 1 (NF1) in children 2 years of age and older.

　　根据有关数据研究发现，司美替尼(Selumetinib)可以抑制NF1小鼠的ERK磷酸化，并减少神经纤维瘤的数量、体积和增殖。

　　但是最好的药物，因为长期的服用后也会产生耐药，司美替尼也不例外。那么，吃司美替尼多久后会耐药？

　　患者服用司美替尼后的耐药时间并没有固定的数值，因为每个患者的病情和身体情况都不一样，服用后的情况也不一样，因此需要因人而异。当患者服用后出现耐药反应，应该及时告知医生，根据医生指导下更换药物。

There is no fixed value for the duration of resistance of patients taking smetinib, because each patient's condition and physical condition are different, and the situation after taking smetinib is also different, so it needs to vary from person to person. When patients have drug resistance reactions after taking the drug, they should inform the doctor in time and change the drug according to the doctor's guidance.