exhibit 10. 1 march 18, 2022 histogen, inc. 10655 sorrento valley road, ste 200 san diego, ca 92121 attn : president allergan sales, llc allergan, inc. 5 giralda farms madison, nj 07940 www. allergan. com march 18, 2022 histogen, inc. 10655 sorrento valley road, ste 200 san diego, ca 92121 attn : president allergan sales, llc allergan, inc. 5 giralda farms madison, nj 07940 www. allergan. com re : the amended and restated license agreement entered into as of december 16, 2013, as amended by the july 2017, october 2017, january 2019, and january 2020 amendments ( collectively, the " license agreement " ), by and between histogen, inc. ( " histogen " ), and allergan sales, llc, ( " allergan " ) re : re : the amended and restated license agreement entered into as of december 16, 2013, as amended by the july 2017, october 2017, january 2019, and january 2020 amendments ( collectively, the " license agreement " ), by and between histogen, inc. ( " histogen " ), and allergan sales, llc, ( " allergan " ) to whom it may concern : this letter sets forth certain understandings and agreements between histogen and allergan with respect to the license agreement. subject to the execution of this letter by both histogen and allergan, allergan shall make a one - time payment equal to three million seven hundred fifty thousand dollars ( $ 3, 750, 000 ) less any applicable withholding taxes ( the " final payment'' ) to histogen on or before march 31, 2022. histogen agrees that the final payment represents a full and final satisfaction of all money due to histogen pursuant to the license agreement, and, except with respect to the final payment, histogen hereby releases allergan from any and all outstanding payment obligations under the license agreement. in partial consideration for the final payment as set forth in this letter, histogen agrees that allergan shall have no further obligations to histogen under the license agreement with respect to sections 4. 4, 4. 5, 7. 1, and