DEUTERIUM-ENRICHED BENDAMUSTINE

1 . A deuterium-enriched compound of formula I or a pharmaceutically acceptable salt thereof:

wherein R 1 -R 21 are independently selected from H and D; and

the abundance of deuterium in R 1 -R 21 is at least 5%.

2 . A deuterium-enriched compound of claim 1 , wherein the abundance of deuterium in R 1 -R 2 , is selected from at least 5%, at least 10%, at least 14%, at least 19%, at least 24%, at least 29%, at least 33%, at least 38%, at least 43%, at least 48%, at least 52%, (k) at least 57%, at least 62%, at least 67%, at least 71%, at least 76%, at least 81%, at least 86%, at least 90%, at least 95%, and 100%.

3 . A deuterium-enriched compound of claim 1 , wherein the abundance of deuterium in R 1 is selected from at least 100%.

4 . A deuterium-enriched compound of claim 1 , wherein the abundance of deuterium in R 2 -R 7 is selected from at least 17%, at least 33%, at least 50%, at least 67%, at least 83%, and 100%.

5 . A deuterium-enriched compound of claim 1 , wherein the abundance of deuterium in R 8 -R 10 is selected from at least 33%, at least 67%, and 100%.

6 . A deuterium-enriched compound of claim 1 , wherein the abundance of deuterium in R 1 -R 13 is selected from at least 33%, at least 67%, and 100%.

7 . A deuterium-enriched compound of claim 1 , wherein the abundance of deuterium in R 14 -R 21 is selected from at least 13%, at least 25%, at least 38%, at least 50%, at least 63%, at least 75%, at least 88%, and 100%.

8 . A deuterium-enriched compound of claim 1 , wherein the compound is selected from compounds 1-6 of Table 1.

9 . A deuterium-enriched compound of claim 1 , wherein the compound is selected from compounds 7-12 of Table 2.

10 . An isolated deuterium-enriched compound of formula I or a pharmaceutically acceptable salt thereof:

wherein R 1 -R 2 , are independently selected from H and D; and

the abundance of deuterium in R 1 -R 21 is at least 5%.

11 . An isolated deuterium-enriched compound of claim 10 , wherein the abundance of deuterium in R 1 -R 21 is selected from at least 5%, at least 10%, at least 14%, at least 19%, at least 24%, at least 29%, at least 33%, at least 38%, at least 43%, at least 48%, at least 52%, (k) at least 57%, at least 62%, at least 67%, at least 71%, at least 76%, at least 81%, at least 86%, at least 90%, at least 95%, and 100%.

12 . An isolated deuterium-enriched compound of claim 10 , wherein the abundance of deuterium in R 1 is selected from at least 100%.

13 . An isolated deuterium-enriched compound of claim 10 , wherein the abundance of deuterium in R 2 -R 7 is selected from at least 17%, at least 33%, at least 50%, at least 67%, at least 83%, and 100%.

14 . An isolated deuterium-enriched compound of claim 10 , wherein the compound is selected from compounds 1-6 of Table 1.

15 . An isolated deuterium-enriched compound of claim 10 , wherein the compound is selected from compounds 7-12 of Table 2.

16 . A mixture of deuterium-enriched compounds of formula I or a pharmaceutically acceptable salt thereof:

wherein R 1 -R 2 , are independently selected from H and D; and

the abundance of deuterium in R 1 -R 21 is at least 5%.

17 . A mixture of deuterium-enriched compound of claim 16 , wherein the compound is selected from compounds 1-6 of Table 1.

18 . A mixture of deuterium-enriched compound of claim 16 , wherein the compound is selected from compounds 7-12 of Table 2.

19 . A pharmaceutical composition, comprising: a pharmaceutically acceptable carrier and a therapeutically effective amount of a compound of claim 1 or a pharmaceutically acceptable salt form thereof.

20 . A method for treating a disease selected from non-hodgkin's lymphoma, small cell lung cancer, lymphocyctic leukemia, breast cancer, and/or multiple myeloma comprising: administering, to a patient in need thereof, a therapeutically effective amount of a compound of claim 1 or a pharmaceutically acceptable salt form thereof.