Item 1. Unaudited Condensed Financial Statements
MUSTANG BIO, INC.
Condensed Balance Sheets
($ in thousands, except for share and per share amounts)
​
| ​ | ​ | ​ | ​ | ​ | ​ | ​ |
| ​ | ​ | September 30, | ​ | December 31, |
| ​ | 2020 | 2019 |
| ​ | ​ | (Unaudited) | ​ | ​ | ​ |
| ASSETS | ​ | ​ |
| Current Assets: | ​ | ​ |
| Cash and cash equivalents | ​ | $ | 75,251 | ​ | $ | 61,413 |
| Other receivables - related party | ​ | 37 | ​ | 19 |
| Prepaid expenses and other current assets | ​ | 344 | ​ | 1,631 |
| Total current assets | ​ | 75,632 | ​ | 63,063 |
| ​ | ​ | ​ |
| Property, plant and equipment, net | ​ | 7,250 | ​ | 6,779 |
| Fixed assets - construction in process | ​ | 821 | ​ | 1,157 |
| Restricted cash | ​ | 1,000 | ​ | 1,000 |
| Other assets | ​ | 250 | ​ | 250 |
| Operating lease right-of-use asset, net | ​ | ​ | 1,115 | ​ | ​ | 1,196 |
| Total Assets | ​ | $ | 86,068 | ​ | $ | 73,445 |
| ​ | ​ | ​ |
| LIABILITIES AND STOCKHOLDERS’ EQUITY | ​ | ​ |
| Current Liabilities: | ​ | ​ |
| Short-term notes payable | ​ | $ | — | ​ | $ | 1,250 |
| Accounts payable and accrued expenses | ​ | ​ | 7,054 | ​ | ​ | 5,668 |
| Payables and accrued expenses - related party | ​ | 305 | ​ | 596 |
| Operating lease liabilities - short-term | ​ | ​ | 271 | ​ | ​ | 257 |
| Total current liabilities | ​ | 7,630 | ​ | 7,771 |
| ​ | ​ | ​ |
| Notes payable | ​ | ​ | — | ​ | ​ | 12,179 |
| Operating lease liabilities - long-term | ​ | ​ | 2,022 | ​ | ​ | 1,843 |
| Total Liabilities | ​ | 9,652 | ​ | 21,793 |
| ​ | ​ | ​ |
| Commitments and Contingencies | ​ | ​ |
| ​ | ​ | ​ |
| Stockholders’ Equity | ​ | ​ |
| Preferred stock ($ 0.0001 par value), 2,000,000 shares authorized, 250,000 shares of Class A preferred stock issued and outstanding as of September 30, 2020 and December 31, 2019, respectively | ​ | — | ​ | — |
| Common Stock ($ 0.0001 par value), 85,000,000 shares authorized | ​ | ​ |
| Class A common shares, 845,385 shares issued and outstanding as of September 30, 2020 and December 31, 2019, respectively | ​ | — | ​ | — |
| Common shares, 60,164,539 and 39,403,519 shares issued and outstanding as of September 30, 2020 and December 31, 2019, respectively | ​ | 5 | ​ | 4 |
| Common stock issuable, 65,810 and 1,206,667 shares as of September 30, 2020 and December 31, 2019, respectively | ​ | 235 | ​ | 4,923 |
| Additional paid-in capital | ​ | 241,042 | ​ | 172,184 |
| Accumulated deficit | ​ | ( 164,866 ) | ​ | ( 125,459 ) |
| Total Stockholders’ Equity | ​ | 76,416 | ​ | 51,652 |
| Total Liabilities and Stockholders’ Equity | ​ | $ | 86,068 | ​ | $ | 73,445 |

​
The accompanying notes are an integral part of these condensed financial statements.
​
3
| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |
| ​ | ​ | For the three months ended September 30, | ​ | For the nine months ended September 30, |
| ​ | 2020 | 2019 | 2020 | 2019 |
| Operating expenses: | ​ | ​ | ​ | ​ |
| Research and development | ​ | $ | 7,987 | ​ | $ | 7,309 | ​ | $ | 27,131 | ​ | $ | 21,092 |
| Research and development – licenses acquired | ​ | 287 | ​ | 700 | ​ | 1,837 | ​ | 1,350 |
| General and administrative | ​ | 2,153 | ​ | 1,987 | ​ | 7,100 | ​ | 7,520 |
| Total operating expenses | ​ | 10,427 | ​ | 9,996 | ​ | 36,068 | ​ | 29,962 |
| Loss from operations | ​ | ( 10,427 ) | ​ | ( 9,996 ) | ​ | ( 36,068 ) | ​ | ( 29,962 ) |
| ​ | ​ | ​ | ​ | ​ |
| Other income (expense) | ​ | ​ | ​ | ​ |
| Interest income | ​ | 162 | ​ | 406 | ​ | 567 | ​ | 945 |
| Interest expense | ​ | ( 2,687 ) | ​ | ( 578 ) | ​ | ( 3,906 ) | ​ | ( 1,163 ) |
| Total other income (expense) | ​ | ( 2,525 ) | ​ | ( 172 ) | ​ | ( 3,339 ) | ​ | ( 218 ) |
| Net Loss | ​ | $ | ( 12,952 ) | ​ | $ | ( 10,168 ) | ​ | $ | ( 39,407 ) | ​ | $ | ( 30,180 ) |
| ​ | ​ | ​ | ​ | ​ | ​ | ​ |
| Net loss per common share outstanding, basic and diluted | ​ | $ | ( 0.23 ) | ​ | $ | ( 0.25 ) | ​ | $ | ( 0.82 ) | ​ | $ | ( 0.87 ) |
| ​ | ​ | ​ | ​ | ​ |
| Weighted average number of common shares outstanding, basic and diluted | ​ | 57,253,715 | ​ | 39,875,209 | ​ | 48,116,158 | ​ | 34,752,938 |

| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |
| ​ | ​ | For the Three Months Ended September 30, 2020 |
| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | Common | ​ | Additional | ​ | ​ | ​ | ​ | Total |
| ​ | ​ | Class A Preferred Stock | ​ | Class A Common Shares | ​ | Common Shares | ​ | Stock | ​ | Paid-in | ​ | Accumulated | ​ | Stockholders' |
| ​ | Shares | Amount | Shares | Amount | Shares | Amount | Issuable | Capital | Deficit | Equity |
| Balances at June 30, 2020 | 250,000 | ​ | $ | — | 845,385 | ​ | $ | — | 54,826,243 | ​ | $ | 5 | ​ | $ | — | ​ | $ | 222,938 | ​ | $ | ( 151,914 ) | ​ | $ | 71,029 |
| Issuance of common shares, net of offering costs - At-the-Market Offering | — | ​ | — | — | ​ | — | 5,044,803 | ​ | — | ​ | — | ​ | 17,240 | ​ | — | ​ | 17,240 |
| Issuance of common shares, equity fee on At-the-Market Offering | — | ​ | — | — | ​ | — | 64,015 | ​ | — | ​ | 235 | ​ | 215 | ​ | — | ​ | 450 |
| Issuance of common shares, net of offering costs - Public Offering | — | ​ | — | — | ​ | — | — | ​ | — | ​ | — | ​ | ( 137 ) | ​ | — | ​ | ( 137 ) |
| Issuance of common shares under ESPP | — | ​ | — | — | ​ | — | 72,505 | ​ | — | ​ | — | ​ | 180 | ​ | — | ​ | 180 |
| Stock-based compensation expenses | — | ​ | — | — | ​ | — | 156,973 | ​ | — | ​ | — | ​ | 606 | ​ | — | ​ | 606 |
| Exercise of warrants | — | ​ | — | — | ​ | — | — | ​ | — | ​ | — | ​ | — | ​ | — | ​ | — |
| Net loss | — | ​ | — | — | ​ | — | — | ​ | — | ​ | — | ​ | — | ​ | ( 12,952 ) | ​ | ( 12,952 ) |
| Balances at September 30, 2020 | 250,000 | ​ | $ | — | 845,385 | ​ | $ | — | 60,164,539 | ​ | $ | 5 | ​ | $ | 235 | ​ | $ | 241,042 | ​ | $ | ( 164,866 ) | ​ | $ | 76,416 |
| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |
| ​ | ​ | For the Nine Months Ended September 30, 2020 |
| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | Common | ​ | Additional | ​ | ​ | ​ | ​ | Total |
| ​ | ​ | Class A Preferred Stock | ​ | Class A Common Shares | ​ | Common Shares | ​ | Stock | ​ | Paid-in | ​ | Accumulated | ​ | Stockholders' |
| ​ | Shares | Amount | Shares | Amount | Shares | Amount | Issuable | Capital | Deficit | Equity |
| Balances at December 31, 2019 | 250,000 | ​ | $ | — | 845,385 | ​ | $ | — | 39,403,519 | ​ | $ | 4 | ​ | $ | 4,923 | ​ | $ | 172,184 | ​ | $ | ( 125,459 ) | ​ | $ | 51,652 |
| Issuance of common shares - Founders Agreement | — | ​ | — | — | ​ | — | 1,206,667 | ​ | — | ​ | ( 4,923 ) | ​ | 4,923 | ​ | — | ​ | — |
| Issuance of common shares, net of offering costs - At-the-Market Offering | — | ​ | — | — | ​ | — | 7,180,437 | ​ | — | ​ | — | ​ | 25,083 | ​ | — | ​ | 25,083 |
| Issuance of common shares, equity fee on At-the-Market Offering | — | ​ | — | — | ​ | — | 117,405 | ​ | — | ​ | 235 | ​ | 417 | ​ | — | ​ | 652 |
| Issuance of common shares, net of offering costs - Public Offering | — | ​ | — | — | ​ | — | 11,455,604 | ​ | 1 | ​ | — | ​ | 34,786 | ​ | — | ​ | 34,787 |
| Issuance of common shares, equity fee on Public Offering | — | ​ | — | — | ​ | — | 286,390 | ​ | — | ​ | — | ​ | 932 | ​ | — | ​ | 932 |
| Issuance of common shares under ESPP | — | ​ | — | — | ​ | — | 140,856 | ​ | — | ​ | — | ​ | 349 | ​ | — | ​ | 349 |
| Stock-based compensation expenses | — | ​ | — | — | ​ | — | 370,662 | ​ | — | ​ | — | ​ | 2,368 | ​ | — | ​ | 2,368 |
| Exercise of warrants | — | ​ | — | — | ​ | — | 2,999 | ​ | — | ​ | — | ​ | — | ​ | — | ​ | — |
| Net loss | — | ​ | — | — | ​ | — | — | ​ | — | ​ | — | ​ | — | ​ | ( 39,407 ) | ​ | ( 39,407 ) |
| Balances at September 30, 2020 | 250,000 | ​ | $ | — | 845,385 | ​ | $ | — | 60,164,539 | ​ | $ | 5 | ​ | $ | 235 | ​ | $ | 241,042 | ​ | $ | ( 164,866 ) | ​ | $ | 76,416 |

| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |
| ​ | ​ | For the Three Months Ended September 30, 2019 |
| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | Common | ​ | Additional | ​ | ​ | ​ | ​ | Total |
| ​ | ​ | Class A Preferred Stock | ​ | Class A Common Shares | ​ | Common Shares | ​ | Stock | ​ | Paid-in | ​ | Accumulated | ​ | Stockholders' |
| ​ | Shares | Amount | Shares | Amount | Shares | Amount | Issuable | Capital | Deficit | Equity |
| Balances at June 30, 2019 | 250,000 | ​ | $ | — | 862,392 | ​ | $ | — | 39,454,316 | ​ | $ | 4 | ​ | $ | — | ​ | $ | 170,522 | ​ | $ | ( 99,082 ) | ​ | $ | 71,444 |
| Issuance of common shares, net of offering costs - Public Offering | ​ | — | ​ | ​ | — | ​ | — | ​ | ​ | — | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 52 | ​ | ​ | — | ​ | ​ | 52 |
| Stock-based compensation expenses | — | ​ | — | — | ​ | — | 96,477 | ​ | — | ​ | — | ​ | 1,120 | ​ | — | ​ | 1,120 |
| Exercise of warrants | — | ​ | — | — | ​ | — | 27,578 | ​ | — | ​ | — | ​ | — | ​ | — | ​ | — |
| Net loss | — | ​ | — | — | ​ | — | — | ​ | — | ​ | — | ​ | — | ​ | ( 10,168 ) | ​ | ( 10,168 ) |
| Balances at September 30, 2019 | 250,000 | ​ | $ | — | 862,392 | ​ | $ | — | 39,578,371 | ​ | $ | 4 | ​ | $ | — | ​ | $ | 171,694 | ​ | $ | ( 109,250 ) | ​ | $ | 62,448 |
| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |
| ​ | ​ | For the Nine Months Ended September 30, 2019 |
| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | Common | ​ | Additional | ​ | ​ | ​ | ​ | Total |
| ​ | ​ | Class A Preferred Stock | ​ | Class A Common Shares | ​ | Common Shares | ​ | Stock | ​ | Paid-in | ​ | Accumulated | ​ | Stockholders' |
| ​ | Shares | Amount | Shares | Amount | Shares | Amount | Issuable | Capital | Deficit | Equity |
| Balances at December 31, 2018 | 250,000 | ​ | $ | — | 1,000,000 | ​ | $ | — | 26,610,183 | ​ | $ | 3 | ​ | $ | 2,085 | ​ | $ | 113,378 | ​ | $ | ( 79,070 ) | ​ | $ | 36,396 |
| Issuance of common shares - Founders Agreement | — | ​ | — | — | ​ | — | 709,314 | ​ | — | ​ | ( 2,085 ) | ​ | 2,085 | ​ | — | ​ | — |
| Issuance of common shares- Equity fee on Horizon Notes to Fortress Biotech | ​ | — | ​ | ​ | — | ​ | — | ​ | ​ | — | ​ | 108,069 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 375 | ​ | ​ | — | ​ | ​ | 375 |
| Issuance of warrants- Horizon Notes | — | ​ | — | — | ​ | — | — | ​ | — | ​ | — | ​ | 888 | ​ | — | ​ | 888 |
| Conversion of Class A Common shares to common shares | ​ | — | ​ | ​ | — | ​ | ( 137,608 ) | ​ | ​ | — | ​ | 137,608 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — |
| Issuance of common shares, net of offering shares -At-the-Market Offering | ​ | — | ​ | ​ | — | ​ | — | ​ | ​ | — | ​ | 3,506,222 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 21,972 | ​ | ​ | — | ​ | ​ | 21,972 |
| Issuance of common shares - Equity fee on At-the-Market Offering | ​ | — | ​ | ​ | — | ​ | — | ​ | ​ | — | ​ | 87,656 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 495 | ​ | ​ | — | ​ | ​ | 495 |
| Issuance of common shares, net of offering costs- Public Offering | ​ | — | ​ | ​ | — | ​ | — | ​ | ​ | — | ​ | 7,906,250 | ​ | ​ | 1 | ​ | ​ | — | ​ | ​ | 29,536 | ​ | ​ | — | ​ | ​ | 29,537 |
| Issuance of common shares- Equity fee on Public Offering | ​ | — | ​ | ​ | — | ​ | — | ​ | ​ | — | ​ | 197,656 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 791 | ​ | ​ | — | ​ | ​ | 791 |
| Stock-based compensation expenses | ​ | — | ​ | ​ | — | ​ | — | ​ | ​ | — | ​ | 222,477 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 2,174 | ​ | ​ | — | ​ | ​ | 2,174 |
| Exercise of warrants | — | ​ | — | — | ​ | — | 92,936 | ​ | — | ​ | — | ​ | — | ​ | — | ​ | — |
| Net loss | — | ​ | — | — | ​ | — | — | ​ | — | ​ | — | ​ | — | ​ | ( 30,180 ) | ​ | ( 30,180 ) |
| Balances at September 30, 2019 | 250,000 | ​ | $ | — | 862,392 | ​ | $ | — | 39,578,371 | ​ | $ | 4 | ​ | $ | — | ​ | $ | 171,694 | ​ | $ | ( 109,250 ) | ​ | $ | 62,448 |

| ​ | ​ | ​ | ​ | ​ | ​ | ​ |
| ​ | ​ | For the nine months ended September 30, |
| ​ | 2020 | 2019 |
| Cash Flows from Operating Activities: | ​ | ​ |
| Net loss | ​ | $ | ( 39,407 ) | ​ | $ | ( 30,180 ) |
| Adjustments to reconcile net loss to net cash used in operating activities: | ​ | ​ | ​ | ​ | ​ | ​ |
| Accretion of debt discount | ​ | 2,321 | ​ | 466 |
| Issuance of common shares - Equity fee on At-the-Market Offering to Fortress Biotech | ​ | 417 | ​ | 495 |
| Issuance of common shares - Equity fee on Public Offering to Fortress Biotech | ​ | ​ | 932 | ​ | ​ | 791 |
| Issuance of common shares - Equity fee on Horizon Notes to Fortress Biotech | ​ | ​ | — | ​ | ​ | 375 |
| Common shares issuable for Founders Agreement | ​ | 235 | ​ | — |
| Research and development - licenses acquired | ​ | ​ | 1,837 | ​ | ​ | 1,350 |
| Stock-based compensation expenses | ​ | 2,368 | ​ | 2,174 |
| Depreciation expense | ​ | 1,223 | ​ | 907 |
| Amortization of operating lease right-of-use assets | ​ | 81 | ​ | 80 |
| Changes in operating assets and liabilities: | ​ | ​ | ​ |
| Prepaid expenses and other current assets | ​ | 1,594 | ​ | ( 440 ) |
| Other receivables - related party | ​ | ​ | ( 325 ) | ​ | ​ | ( 55 ) |
| Accounts payable and accrued expenses | ​ | 978 | ​ | ( 203 ) |
| Payable and accrued expenses - related party | ​ | ( 291 ) | ​ | 48 |
| Lease liabilities | ​ | ​ | 193 | ​ | ​ | 101 |
| Net cash used in operating activities | ​ | ( 27,844 ) | ​ | ( 24,091 ) |
| ​ | ​ | ​ |
| Cash Flows from Investing Activities: | ​ | ​ |
| Maturity of certificate of deposit | ​ | — | ​ | 17,604 |
| Purchase of research and development licenses | ​ | ( 1,720 ) | ​ | ( 850 ) |
| Purchase of fixed assets | ​ | ( 1,228 ) | ​ | ( 1,454 ) |
| Net cash (used in) provided by investing activities | ​ | ( 2,948 ) | ​ | 15,300 |
| ​ | ​ | ​ |
| Cash Flows from Financing Activities: | ​ | ​ |
| Proceeds from Horizon Notes | ​ | — | ​ | 15,000 |
| Debt issuance costs | ​ | ​ | — | ​ | ​ | ( 1,393 ) |
| Proceeds from issuance of common shares - At-the-Market Offering | ​ | ​ | 25,570 | ​ | ​ | 22,515 |
| Offering costs for the issuance of common shares - At-the-Market Offering | ​ | ​ | ( 487 ) | ​ | ​ | ( 543 ) |
| Proceeds from issuance of common shares - Public Offering | ​ | ​ | 37,230 | ​ | ​ | 31,625 |
| Offering costs for the issuance of common shares - Public Offering | ​ | ​ | ( 2,282 ) | ​ | ​ | ( 2,088 ) |
| Repayment of notes payable | ​ | ​ | ( 15,750 ) | ​ | ​ | — |
| Proceeds from issuance of common shares under ESPP | ​ | ​ | 349 | ​ | ​ | — |
| Net cash provided by financing activities | ​ | 44,630 | ​ | 65,116 |
| ​ | ​ | ​ |
| Net change in cash, cash equivalents and restricted cash | ​ | 13,838 | ​ | 56,325 |
| Cash, cash equivalents and restricted cash, beginning of the period | ​ | 62,413 | ​ | 16,969 |
| Cash, cash equivalents and restricted cash, end of the period | ​ | $ | 76,251 | ​ | $ | 73,294 |
| ​ | ​ | ​ |
| Supplemental disclosure of cash flow information: | ​ | ​ |
| Cash paid for interest | ​ | $ | 1,577 | ​ | $ | 698 |
| ​ | ​ | ​ |
| Supplemental disclosure of noncash investing and financing activities: | ​ | ​ |
| Fixed assets (acquired but not paid) | ​ | $ | 317 | ​ | $ | 288 |
| Issuance of common shares - Founders Agreement | ​ | $ | 4,923 | ​ | $ | 2,085 |
| Research and development licenses included in accounts payable and accrued expenses | ​ | $ | 117 | ​ | $ | 500 |
| Offering costs for the issuance of common shares - Public Offering, in accounts payable and accrued expenses | ​ | $ | 161 | ​ | $ | — |
| Issuance of warrants - Horizon Notes | ​ | $ | — | ​ | $ | 888 |

Note 1 - Organization, Description of Business and Liquidity and Capital ResourcesMustang Bio, Inc. (the “Company” or “Mustang”) was incorporated in Delaware on March 13, 2015. Mustang is as a clinical-stage biopharmaceutical company focused on translating today’s medical breakthroughs in cell and gene therapy into potential cures for hematologic cancers, solid tumors and rare genetic diseases. The Company may acquire rights to these technologies by licensing the rights or otherwise acquiring an ownership interest in the technologies, funding their research and development and eventually either out-licensing or bringing the technologies to market.The Company is a majority-controlled subsidiary of Fortress Biotech, Inc. (“Fortress” or “Parent”).Liquidity and Capital ResourcesThe Company has incurred substantial operating losses and expects to continue to incur significant operating losses for the foreseeable future and may never become profitable. As of September 30, 2020, the Company had an accumulated deficit of $ 164.9 million.The Company has funded its operations to date primarily through the sale of equity and its venture debt financing agreement (the “Loan Agreement”) with Horizon Technology Finance Corporation (“Horizon”), herein referred to as the “Horizon Notes.” The Company expects to continue to use the proceeds from previous financing transactions primarily for general corporate purposes, including financing the Company’s growth, developing new or existing product candidates, and funding capital expenditures, acquisitions and investments. The Company currently anticipates that its cash and cash equivalents balances at September 30, 2020, are sufficient to fund its anticipated operating cash requirements for at least one year from the date of this Form 10-Q.The Company will be required to expend significant funds in order to advance the development of its product candidates. The Company will require additional financings through equity and debt offerings, collaborations and licensing arrangements or other sources to fully develop, prepare regulatory filings, obtain regulatory approvals and commercialize its existing and any new product candidates. In addition to the foregoing, based on the Company’s current assessment, the Company does not expect any material impact on its long-term development timeline and its liquidity due to the worldwide spread of the COVID-19 virus. However, the Company is continuing to assess the effect on its operations by monitoring the spread of COVID-19 and the actions implemented to combat the virus throughout the world. ​ Note 2 - Significant Accounting Policies Basis of PresentationThe accompanying unaudited interim condensed financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) for interim financial information and the instructions to Form 10-Q and Article 10 of Regulation S-X of the Exchange Act. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, the unaudited interim condensed financial statements reflect all adjustments, which include only normal recurring adjustments necessary for the fair statement of the balances and results for the periods presented. They may not include all of the information and footnotes required by GAAP for complete financial statements. Therefore, these financial statements should be read in conjunction with the Company's audited financial statements and notes thereto for the year ended December 31, 2019, which were included in the Company’s Form 10-K and filed with the SEC on March 16, 2020. The results of operations for any interim periods are not necessarily indicative of the results that may be expected for the entire fiscal year or any other interim period. Use of EstimatesThe Company’s unaudited condensed financial statements include certain amounts that are based on management’s best estimates and judgments. The Company’s significant estimates include, but are not limited to, assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. Due to the uncertainty inherent in such estimates actual results could differ from those estimates. 8
| ​ | ​ | ​ | ​ | ​ |
| ​ | ​ | For the nine months ended September 30, |
| ​ | 2020 | 2019 |
| Warrants | 5,402,670 | 5,405,946 |
| Options | 1,141,675 | 1,241,675 |
| Class A Preferred Shares | 250,000 | 250,000 |
| Unvested restricted stock awards | 302,114 | 571,696 |
| Unvested restricted stock units | 1,500,310 | 932,917 |
| Total | 8,596,769 | 8,402,234 |

| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |
| ​ | ​ | For the three months ended September 30, | ​ | For the nine months ended September 30, |
| ($ in thousands) | 2020 | 2019 | 2020 | 2019 |
| City of Hope National Medical Center | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |
| CD123 | ​ | $ | — | ​ | $ | — | ​ | $ | 334 | ​ | $ | 250 |
| CS1 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 200 |
| IL13Rα2 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 333 | ​ | ​ | — |
| Spacer | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 333 | ​ | ​ | — |
| PSCA | ​ | ​ | — | ​ | ​ | 200 | ​ | ​ | — | ​ | ​ | 200 |
| HER2 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 250 | ​ | ​ | — |
| CSL Behring (Calimmune) | ​ | ​ | 170 | ​ | ​ | 200 | ​ | ​ | 170 | ​ | ​ | 200 |
| UCLA | ​ | ​ | — | ​ | ​ | 300 | ​ | ​ | — | ​ | ​ | 300 |
| Fred Hutchinson Cancer Research Center - CD20 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 300 | ​ | ​ | — |
| Nationwide Children's Hospital - C134 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 200 |
| SIRION Biotech LentiBOOSTTM | ​ | ​ | 117 | ​ | ​ | — | ​ | ​ | 117 | ​ | ​ | — |
| Total | ​ | $ | 287 | ​ | $ | 700 | ​ | $ | 1,837 | ​ | $ | 1,350 |

For the nine months ended, September 30, 2020, the Company expensed a non-refundable milestone payment of $ 0.3 million in connection with Mustang’s public underwritten offerings.HER2 License (MB-103)On May 31, 2017, the Company entered into an exclusive license agreement with COH for the use of human epidermal growth factor receptor 2 (“HER2”) CAR T technology, which will initially be applied in the treatment of glioblastoma multiforme. Pursuant to this agreement, additional payments are due for the achievement of ten development milestones totaling $ 14.9 million, and royalty payments in the mid-single digits are due on net sales of licensed products.For the nine months ended, September 30, 2020, the Company expensed a non-refundable milestone payment of $ 0.3 million in connection with the twelfth patient treated in the Phase 1 clinical study of HER2 CAR T technology at COH.CSL Behring (Calimmune) On August 23, 2019, the Company entered into a Non-Exclusive License Agreement with Calimmune, Inc. (“Calimmune License”) for the rights to the cell bank to be used in the manufacture of the X-linked Severe Combined Immunodeficiency (“XSCID”) vector that was separately licensed from St. Jude Children’s Research Hospital, Inc. (“St. Jude”) in August 2018. Pursuant to the terms of the Calimmune License the Company paid an upfront fee of $ 0.2 million. Upon the achievement of three development milestones, fees totaling $ 1.0 million will be due. Royalty payments in the low-single digits are due on net sales of licensed products.​For the three and nine months ended, September 30, 2020, the Company recorded research and development expense of $ 0.2 million in connection with the Calimmune License.​Fred Hutchinson Cancer Research Center - CD20 License (MB-106)On July 3, 2017, Mustang entered into an exclusive, worldwide licensing agreement with Fred Hutchinson Cancer Research Center (“Fred Hutch”) for the use of a CAR T therapy related to autologous T cells engineered to express a CD20-specific chimeric antigen receptor (“CD20 Technology License”). Pursuant to the CD20 Technology License, the Company paid Fred Hutch an upfront fee of $ 0.3 million and will owe an annual maintenance fee of $ 50,000 on each anniversary of the license until the achievement by the Company of regulatory approval of a licensed product using CD20 Technology. Additional payments are due for the achievement of eleven development milestones totaling $ 39.1 million and royalty payments in the mid-single digits are due on net sales of licensed products.For the nine months ended, September 30, 2020, the Company expensed a non-refundable milestone payment of $ 0.3 million in connection with the twelfth patient treated in the Phase 1 clinical study of CD20 CAR T technology at Fred Hutch.SIRION Biotech GmbH - LentiBOOSTTMOn September 30, 2020, Mustang entered into an exclusive, worldwide licensing agreement with SIRION Biotech (“SIRION”) for the rights to SIRION’s LentiBOOSTTM technology for the development of MB-207, Mustang’s lentiviral gene therapy for the treatment of previously transplanted XSCID patients (the “SIRION Technology License”). Pursuant to the SIRION Technology License, the Company paid SIRION a one-time upfront fee of $ 0.1 million (€ 0.1 million) during the three and nine months ended September 30, 2020. In addition, five future development milestone payments totaling up to approximately $ 5.6 million (€ 4.7 million) in the aggregate are due upon achievement of certain milestones. Additional milestone payments totaling up to $ 4.1 million (€ 3.5 million) in the aggregate are due in connection with the achievement of three commercial milestones and low- to mid-single digit royalties are due on aggregate cumulative worldwide net sales of licensed products.For the three and nine months ended, September 30, 2020, the Company expensed an up-front payment of $ 0.1 million. 11
| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |
| ​ | ​ | For the three months ended September 30, | ​ | For the nine months ended September 30, |
| ($ in thousands) | 2020 | 2019 | 2020 | 2019 |
| City of Hope National Medical Center | ​ | ​ | — | ​ | ​ | 500 | ​ | ​ | 500 | ​ | ​ | 1,500 |
| CD123 | ​ | ​ | 48 | ​ | ​ | 269 | ​ | ​ | 344 | ​ | ​ | 1,028 |
| IL13Rα2 | ​ | ​ | 96 | ​ | ​ | 244 | ​ | ​ | 422 | ​ | ​ | 811 |
| Manufacturing | ​ | ​ | — | ​ | ​ | 114 | ​ | ​ | — | ​ | ​ | 343 |
| CS1 | ​ | ​ | 65 | ​ | ​ | — | ​ | ​ | 835 | ​ | ​ | — |
| Fred Hutchinson Cancer Research Center - CD20 | ​ | ​ | 418 | ​ | ​ | 49 | ​ | ​ | 1,134 | ​ | ​ | 690 |
| St. Jude Children's Research Hospital - XSCID | ​ | ​ | 107 | ​ | ​ | — | ​ | ​ | 1,665 | ​ | ​ | — |
| Beth Israel Deaconess Medical Center - CRISPR | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 69 |
| Total | ​ | ​ | 734 | ​ | ​ | 1,176 | ​ | ​ | 4,900 | ​ | ​ | 4,441 |

| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |
| ​ | Estimated Useful | September 30, | December 31, |
| ($ in thousands) | ​ | Life (in years) | ​ | 2020 | ​ | 2019 |
| Computer equipment | 3 | ​ | $ | 68 | ​ | $ | 53 |
| Furniture and fixtures | 5 | ​ | 182 | ​ | 145 |
| Machinery and equipment | 5 | ​ | 5,014 | ​ | 4,594 |
| Leasehold improvements | 9 | ​ | 5,099 | ​ | 3,877 |
| Construction in process | N/A | ​ | 821 | ​ | 1,157 |
| Total property and equipment | ​ | ​ | ​ | 11,184 | ​ | 9,826 |
| Less: accumulated depreciation | ​ | ​ | ​ | ( 3,113 ) | ​ | ( 1,890 ) |
| Property and equipment, net | ​ | ​ | ​ | $ | 8,071 | ​ | $ | 7,936 |
| ​ | ​ | ​ | ​ | ​ | ​ | ​ |
| ​ | ​ | September 30, | ​ | December 31, |
| ($ in thousands) | ​ | 2020 | 2019 |
| Accounts payable | ​ | $ | 3,425 | ​ | $ | 1,877 |
| Research and development | ​ | ​ | 1,821 | ​ | ​ | 1,760 |
| Accrued compensation | ​ | ​ | 1,628 | ​ | ​ | 1,496 |
| Other | ​ | ​ | 180 | ​ | ​ | 535 |
| Total accounts payable and accrued expenses | ​ | $ | 7,054 | ​ | $ | 5,668 |

| ​ | ​ | ​ | ​ | ​ | ​ | ​ |
| ​ | For the Nine Months Ended |
| ​ | ​ | ​ | September 30, | ​ | ​ | September 30, |
| ($ in thousands) | 2020 | 2019 |
| Lease cost | ​ | ​ |
| Operating lease cost | $ | 254 | $ | 235 |
| Variable lease cost | ​ | ​ | 323 | ​ | ​ | 487 |
| Total | $ | 577 | $ | 722 |
| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |
| ​ | For the Nine Months Ended |
| ​ | ​ | ​ | September 30, | ​ | ​ | ​ | September 30, | ​ |
| ($ in thousands) | 2020 | 2019 |
| Operating cash flows from operating leases | $ | ( 41 ) | ​ | $ | 52 | ​ |
| Weighted-average remaining lease term – operating leases | ​ | ​ | 3.4 | ​ | ​ | ​ | 4.5 | ​ |
| Weighted-average discount rate – operating leases | ​ | ​ | 8.98 | % | ​ | ​ | 8.96 | % |
| ​ | ​ | ​ | ​ |
| ($ in thousands) | ​ | ​ |
| Three months ended December 31, 2020 | ​ | $ | 117 |
| Year ended December 31, 2021 | ​ | ​ | 467 |
| Year ended December 31, 2022 | ​ | 475 |
| Year ended December 31, 2023 | ​ | 489 |
| Year ended December 31, 2024 | ​ | 503 |
| Thereafter | ​ | ​ | 955 |
| Total | ​ | 3,006 |
| Less present value discount | ​ | ​ | ( 713 ) |
| Operating lease liabilities | ​ | $ | 2,293 |

| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |
| ​ | ​ | September 30, | December 31, | ​ | ​ |
| ($ in thousands) | 2020 | 2019 | Interest Rate | Maturity |
| Horizon Notes (1)(2) | $ | — | $ | 15,750 | ​ | 9.00 | % | October - 2022 |
| Discount on notes payable | ​ | ​ | — | ​ | ​ | ( 2,321 ) | ​ | ​ | ​ | ​ |
| Total notes payable | $ | — | $ | 13,429 | ​ | ​ | ​ | ​ |
| Less: current portion | ​ | ​ | — | ​ | ​ | ( 1,250 ) | ​ | ​ | ​ | ​ |
| Long-term notes payable | $ | — | $ | 12,179 | ​ | ​ | ​ | ​ |
| (1) | Balance includes $ 0.75 million final payment fee |
| (2) | Interest rate is 9.00 % plus one-month LIBOR Rate in excess of 2.5 % |

In June 2020, the Company issued 286,390 shares of common stock to Fortress, which equaled 2.5 % of the gross proceeds of $ 37.2 million from the sale of shares of common stock, before deducting underwriting discounts and commissions and offering expenses under Mustang’s Public Offering. The Company recorded an expense of approximately $ 0.9 million in general and administrative expenses related to these shares during the nine months ended September 30, 2020.In September 2020, the Company issued 64,015 shares of common stock and recorded 65,810 shares issuable to Fortress, which equaled 2.5 % of the gross proceeds of $ 18.0 million from the sale of shares of common stock under Mustang’s At-the-Market Offering. The Company recorded an expense of approximately $ 0.5 million in general and administrative expenses related to these shares during the nine months ended September 30, 2020.​At-the-Market OfferingOn July 13, 2018, the Company filed a shelf registration statement No. 333-226175 on Form S-3, as amended on July 20, 2018 (the “2018 Mustang S-3”), which was declared effective in August 2018. Under the 2018 Mustang S-3, the Company may sell up to a total of $ 75.0 million of its securities. In connection with the 2018 Mustang S-3, the Company entered into an At-the-Market Issuance Sales Agreement (the “Mustang ATM”) with B. Riley FBR, Inc., Cantor Fitzgerald & Co., National Securities Corporation, and Oppenheimer & Co. Inc. (each an "Agent" and collectively, the “Agents”), relating to the sale of shares of common stock. Under the Mustang ATM, the Company pays the Agents a commission rate of up to 3.0 % of the gross proceeds from the sale of any shares of common stock.On August 16, 2019, the Company filed a shelf registration statement No. 333-233350 on Form S-3, (the “2019 Mustang S-3”), which was declared effective on September 30, 2019. Under the 2019 Mustang S-3, the Company may sell up to a total of $ 75.0 million of its securities.During the nine months ended September 30, 2020, we issued approximately 7.2 million shares of common stock at an average price of $ 3.56 per share for gross proceeds of $ 25.6 million under the Mustang ATM. In connection with these sales, we paid aggregate fees of approximately $ 0.5 million for net proceeds of approximately $ 25.1 million. During the nine months ended September 30, 2019, we issued approximately 3.5 million shares of common stock at an average price of $ 6.42 per share for gross proceeds of $ 22.5 million under the Mustang ATM. In connection with these sales, Mustang paid aggregate fees of approximately $ 0.5 million for net proceeds of approximately $ 22.0 million. ​Pursuant to the Founders Agreement, we issued 183,215 shares of common stock to Fortress at a weighted average price of $ 3.56 per share for the nine months ended September 30, 2020, in connection with the Mustang ATM. During the nine months ended September 30, 2019, we issued 87,656 shares of common stock to Fortress at a weighted average price of $ 6.42 per share in connection with the Mustang ATM.​Public Offering of Common Stock On June 11, 2020, we entered into an underwriting agreement (the “Underwriting Agreement”) with Cantor Fitzgerald & Co., as representative of the underwriters named therein (each, an “Underwriter” and collectively with Cantor Fitzgerald & Co., the “Underwriters”). ​In connection with the Underwriting Agreement, we issued 10,769,231 shares of common stock (plus a 30-day option to purchase up to an additional 1,615,384 shares of common stock, of which 686,373 were exercised as of September 30, 2020) at a price of $ 3.25 per share for gross proceeds of approximately $ 37.2 million, before deducting underwriting discounts and commissions and offering expenses. In connection with the public offering, we paid aggregate fees of approximately $ 2.3 million for net proceeds of approximately $ 34.9 million. The shares were sold under our S-3 registrations filed with the Securities and Exchange Commission. The offering closed on June 15, 2020, and the over-allotment closed on June 25, 2020. As of September 30, 2020, approximately $ 32.6 million of the 2019 Mustang S-3 remains available for sales of securities. Mustang may offer the securities under the 2019 Mustang S-3 from time to time in response to market conditions or other circumstances if it believes such a plan of financing is in the best interests of its stockholders. As of September 30, 2020, the 2018 Mustang S-3 is no longer available for sales of securities. 16
| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |
| ​ | ​ | ​ | ​ | Weighted Average |
| ​ | ​ | ​ | ​ | ​ | ​ | ​ | Remaining |
| ​ | ​ | ​ | ​ | Weighted Average | ​ | Contractual Life (in |
| ​ | ​ | Stock Options | ​ | Exercise Price | ​ | years) |
| Outstanding at December 31, 2019 | 1,241,675 | ​ | $ | 5.73 | 7.31 |
| Options forfeited | ( 100,000 ) | ​ | 5.73 | — |
| Outstanding at September 30, 2020 | 1,141,675 | ​ | 5.73 | 6.56 |
| Options vested and exercisable at September 30, 2020 | 606,514 | ​ | $ | 5.73 | 6.56 |
| ​ | ​ | ​ | ​ | ​ | ​ |
| ​ | ​ | Weighted Average |
| ​ | ​ | ​ | ​ | Grant Date Fair |
| ​ | ​ | Number of Shares | ​ | Value |
| Nonvested at December 31, 2019 | 299,060 | ​ | $ | 5.66 |
| Granted | ​ | 83,055 | ​ | ​ | 3.08 |
| Vested | ​ | ( 80,001 ) | ​ | ​ | 5.73 |
| Nonvested at September 30, 2020 | 302,114 | ​ | $ | 4.93 |

| ​ | ​ | ​ | ​ | ​ | ​ |
| ​ | ​ | Weighted Average |
| ​ | ​ | ​ | ​ | Grant Date Fair |
| ​ | ​ | Number of Units | ​ | Value |
| Nonvested at December 31, 2019 | 1,112,417 | ​ | $ | 5.11 |
| Granted | 809,000 | ​ | 2.94 |
| Forfeited | ​ | ( 129,000 ) | ​ | ​ | 4.47 |
| Vested | ( 292,107 ) | ​ | 4.94 |
| Nonvested at December 31, 2020 | 1,500,310 | ​ | $ | 4.03 |
| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |
| ​ | ​ | For the three months ended September 30, | ​ | For the nine months ended September 30, |
| ​ | 2020 | 2019 | 2020 | 2019 |
| General and administrative | ​ | $ | 348 | ​ | $ | 389 | ​ | $ | 1,213 | ​ | $ | 1,058 |
| Research and development | ​ | 258 | ​ | 731 | ​ | 1,155 | ​ | 1,116 |
| Total stock-based compensation expense | ​ | $ | 606 | ​ | $ | 1,120 | ​ | $ | 2,368 | ​ | $ | 2,174 |
| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |
| ​ | ​ | ​ | ​ | Weighted Average |
| ​ | ​ | ​ | ​ | ​ | ​ | ​ | Remaining |
| ​ | ​ | ​ | ​ | Weighted Average | ​ | Contractual Life (in |
| ​ | ​ | Warrants | ​ | Exercise Price | ​ | years) |
| Outstanding as of December 31, 2019 | 5,405,669 | ​ | $ | 8.20 | 2.40 |
| Cashless exercised | ( 2,999 ) | ​ | — | — |
| Outstanding as of December 31, 2020 | 5,402,670 | ​ | $ | 8.21 | 1.64 |

​
Item 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations
​
Forward-Looking Statements
​
You should read the following discussion and analysis of our financial condition and results of operations in conjunction with our consolidated financial statements and the related notes included elsewhere in this Form 10-Q. Our consolidated financial statements have been prepared in accordance with U.S. GAAP. The following discussion and analysis contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934 (the “Exchange Act”), including, without limitation, statements regarding our expectations, beliefs, intentions or future strategies that are signified by the words “expect,” “anticipate,” “intend,” “believe,” “may,” “plan”, “seek” or similar language. All forward-looking statements included in this document are based on information available to us on the date hereof, and we assume no obligation to update any such forward-looking statements. Our business and financial performance are subject to substantial risks and uncertainties. Actual results could differ materially from those projected in the forward-looking statements. In evaluating our business, you should carefully consider the information set forth under the heading “Risk Factors” herein.
​
Overview
​
Mustang Bio, Inc. (“Mustang,” “We,” “Us” or the “Company”) is a clinical-stage biopharmaceutical company focused on translating today’s medical breakthroughs in cell and gene therapies into potential cures for hematologic cancers, solid tumors and rare genetic diseases. We aim to acquire rights to these technologies by licensing or otherwise acquiring an ownership interest in the technologies, funding their research and development and eventually either out-licensing or bringing the technologies to market.
​
Our pipeline is currently focused in three core areas: gene therapy programs for rare genetic disorders, chimeric antigen receptor (“CAR”) engineered T cell (“CAR T”) therapies for hematologic malignancies and CAR T therapies for solid tumors. For each therapy we have partnered with world class research institutions. For our gene therapy program, we have partnered with St. Jude Children’s Research Hospital (“St. Jude”) in the development of a first-in-class ex vivo lentiviral treatment of X-linked severe combined immunodeficiency (“XSCID”), and for our CAR T therapies we have partnered with the City of Hope National Medical Center (“COH”), Fred Hutchinson Cancer Research Center (“Fred Hutch”) and Nationwide Children’s Hospital (“Nationwide”).
​
Gene Therapy
​
In partnership with St. Jude and the National Institutes of Health (“NIH”), our gene therapy program is being conducted under an exclusive license to develop a potentially curative treatment for XSCID, a rare genetic immune system condition also known as bubble boy disease in which affected patients do not live beyond infancy without treatment. This first-in-class ex vivo lentiviral gene therapy is currently in two Phase 1/2 clinical trials involving two different autologous cell products: a multicenter trial of the MB-107 product in newly diagnosed infants sponsored by St. Jude and a single-center trial of the MB-207 product in previously transplanted patients sponsored by the NIH.
​
In August 2020, we announced that the U.S. Food and Drug Administration (“FDA”) had granted Rare Pediatric Disease Designation to both MB-107 and MB-207. In September 2020 we announced that the FDA had granted Orphan Drug Designation to both MB-107 and MB-207. In April 2020, we announced that the European Medicines Agency (“EMA”) had granted Advanced Therapy Medicinal Product (“ATMP”) classification to MB-107. The FDA previously granted Regenerative Medicine Advanced Therapy (“RMAT”) designation to MB-107 in August 2019.
​
In May 2020, we submitted an IND application with the FDA to initiate a registrational multicenter Phase 2 clinical trial of MB-107 in newly diagnosed infants with XSCID who are under the age of two. The trial is expected to enroll 10 patients who, together with 15 patients enrolled in the current multicenter trial led by St. Jude Children’s Research Hospital, will be compared with 25 matched historical control patients who have undergone hematopoietic stem cell transplant (“HSCT”). The primary efficacy endpoint will be event-free survival. The initiation of this trial is currently on hold pending
19
CMC clearance by the FDA, and this clearance is expected in the first quarter of 2021. We are targeting topline data from the trial in the fourth quarter of 2022.​We further expect to file an IND in the first quarter of 2021 for a registrational multicenter Phase 2 clinical trial of lentiviral gene therapy in previously transplanted XSCID patients (MB-207). We anticipate enrolling 20 patients and comparing them to matched historical control patients who have undergone a second HSCT. We are targeting topline data for this trial in the fourth quarter of 2022.​CAR T Therapies​Our pipeline of CAR T therapies is being developed under exclusive licenses from several world class research institutions. Our strategy is to license these technologies, support preclinical and clinical research activities by our partners and transfer the underlying technology to our cell processing facility located in Worcester, Massachusetts, to conduct our own clinical trials.​We are developing CAR T therapies for hematologic malignancies in partnership with COH targeting CD123 (MB-102) and CS1 (MB-104) and with Fred Hutch targeting CD20 (MB-106). Phase 1 clinical trials sponsored by COH for MB-102 and MB-104 and by Fred Hutch for MB-106 are underway. In the third quarter of 2019 the FDA approved our IND application to initiate a multicenter Phase 1/2 clinical trial of MB-102, and our clinical trial has begun enrollment for the treatment of patients with acute myeloid leukemia (AML), blastic plasmacytoid dendritic cell neoplasm (BPDCN), and high-risk myelodysplastic syndrome (hrMDS). We expect to file an IND application for MB-106 in the first quarter of 2021 and to initiate our own Phase 1 clinical trials shortly thereafter for the treatment of patients with non-Hodgkin lymphoma and chronic lymphocytic leukemia.​We are also developing CAR T therapies for solid tumors in partnership with COH targeting IL13Ra2 (MB-101), HER2 (MB-103) and prostate stem cell antigen (“PSCA”) (MB-105). In addition, we have partnered with Nationwide for the C134 oncolytic virus (MB-108) in order to enhance the activity of MB-101 for the treatment of patients with glioblastoma multiforme (GBM). Phase 1 clinical trials sponsored by COH for MB-101, MB-103 and MB-105 are underway. A Phase 1 clinical trial sponsored by the University of Alabama at Birmingham (“UAB”) for MB-108 began during the third quarter of 2019. In late 2020, COH plans to file IND applications for the combination of MB-101 and MB-108 for the treatment of patients with GBM and for MB-101 alone for the treatment of GBM with leptomeningeal involvement. We also plan to file IND applications and initiate our own clinical trials for MB-103 for the treatment of patients with metastatic breast cancer to brain and for MB-105 for the treatment of patients with prostate and pancreatic cancer.​Recent Events​MB-102 (CD123-targeted CAR T cell therapy)​In October 2020, we announced that the first patient has been dosed in a Mustang-sponsored, open label, multicenter Phase 1/2 clinical trial to evaluate the safety and efficacy of MB-102 in patients with relapsed or refractory BPDCN, AML and hrMDS. Study sites include City of Hope, where the CAR T cell therapy was initially developed and where the clinical data were generated to support Mustang’s current multicenter trial, Dana-Farber Cancer Institute, Duke University and MD Anderson Cancer Center.​The Phase 1 portion of the trial will determine the maximum tolerated dose of MB-102 for the Phase 2 portion of the trial. Safety will be assessed at each dose level before proceeding to the next. The Phase 2 portion of the trial may be divided into as many as three arms to evaluate the efficacy of MB-102 in relapsed or refractory BPDCN (Arm 1), relapsed or refractory AML (Arm 2) and demethylation resistant hrMDS (Arm 3). The primary outcome that will be studied is the response rate at day 28 post infusion in all arms. Secondary outcome measures include duration of response, progression-free survival, overall survival and incidence of treatment-emergent adverse events, which will be followed for up to three years.​20
MB-107 (Ex vivo Lentiviral Therapy for X-linked Severe Combined Immunodeficiency (XSCID))​In August 2020, we announced that the FDA has granted Rare Pediatric Disease Designation to MB-107, Mustang’s lentiviral gene therapy for the treatment of XSCID in newly-diagnosed infants. The FDA previously granted Regenerative Medicine Advanced Therapy designation to MB-107 for the treatment of XSCID in newly-diagnosed infants in August 2019. Additionally, the European Medicines Agency granted Advanced Therapy Medicinal Product classification to MB-107 in April 2020. ​The FDA grants Rare Pediatric Disease Designation for serious and life-threatening diseases that primarily affect children ages 18 years or younger and affect fewer than 200,000 people in the United States. If Mustang’s Biologics License Application is approved, the company may be eligible to receive a priority review voucher, which can be redeemed to obtain priority review for any subsequent marketing application and may be sold or transferred. This program is intended to encourage development of new drugs and biologics for the prevention and treatment of rare pediatric diseases.​In September 2020 we announced that the FDA has granted Orphan Drug Designation to MB-107. The FDA grants Orphan Drug Designation to drugs and biologics that are intended for the safe and effective treatment, diagnosis or prevention of rare diseases or disorders that affect fewer than 200,000 people in the U.S. Orphan Drug Designation provides certain incentives, such as tax credits toward the cost of clinical trials and prescription drug user fee waivers. If a product holding Orphan Drug Designation receives the first FDA approval for the disease in which it has such designation, the product is entitled to seven years of market exclusivity, which is independent from intellectual property protection.MB-105 (PSCA CAR T for Prostate & Pancreatic Cancers)​In October 2020, we announced that one patient’s experience on the Phase 1 trial of MB-105 was presented at the virtual 27th Annual Prostate Cancer Foundation Scientific Retreat. In a 73-year-old male patient with PSCA-positive metastatic castrate-resistant prostate cancer who was treated with MB-105 and lymphodepletion (a standard CAR T pre-conditioning regimen) after failing eight prior therapies, MB-105 demonstrated on day 28 a 94 percent reduction in prostate-specific antigen (PSA), near complete reduction of measurable soft tissue metastasis by computerized tomography, and improvement in bone metastases by magnetic resonance imaging. The therapy was associated with cytokine release syndrome, which was clinically managed with tocilizumab (anti-IL-6 receptor antibody), and hemorrhagic cystitis requiring transfusion which clinically resolved in 30 days.MB-207 (Ex vivo Lentiviral Therapy for X-linked Severe Combined Immunodeficiency (XSCID))​In August 2020, we announced that the FDA has granted Rare Pediatric Disease Designation to MB-207, Mustang’s lentiviral gene therapy for the treatment of patients with XSCID who were previously treated with a hematopoietic stem cell transplantation and for whom re-treatment is indicated. In September 2020, we announced that the FDA has granted Orphan Drug Designation to MB-207. MB-106 (CD20 CAR T for Non-Hodgkin Lymphoma and Chronic Lymphocytic Leukemia)On November 4, 2020, we announced that interim Phase 1/2 data on MB-106, a CD20-targeted, autologous CAR T cell therapy for patients with relapsed or refractory B-cell non-Hodgkin lymphomas, have been selected for a poster presentation on December 5, 2020, at the 62nd American Society of Hematology (ASH) Annual Meeting. In the abstract posted on the ASH website, Fred Hutch reported on an initial seven patients treated without response, followed by a major revision in the cell manufacturing process that was associated with complete remissions in 2 follicular lymphoma patients (one each at dose levels 1 and 2), a partial remission in a mantle cell lymphoma patient at dose level 2, and progressive disease in a follicular lymphoma patient at dose level 1. Dose level 1 was 3.3 x 105 CAR-T cells/kg and dose level 2 was 1 x 106 CAR-T cells/kg. Among the 11 patients reported in the abstract, there was one occurrence of cytokine release syndrome (grade 3 – unexplained alkaline phosphatase elevation in the setting of fever in a patient treated prior to cell process revision) and no occurrences of immune effector cell-associated neurotoxicity syndrome (any grade). No dose-limiting toxicity was observed.21
SIRION Biotech GmbH – LentiBOOSTTMOn September 30, 2020, Mustang entered into an exclusive, worldwide licensing agreement with SIRION Biotech (“SIRION”) for the rights to SIRION’s LentiBOOSTTM technology for the development of MB-207, Mustang’s lentiviral gene therapy for the treatment of previously transplanted XSCID patients (the “SIRION Technology License”). Pursuant to the SIRION Technology License, the Company paid a one-time upfront fee of €0.1 million ($0.1 million) during the three and nine months ended September 30, 2020. In addition, five future development milestone payments totaling up to approximately €4.7 million ($5.5 million) in the aggregate are due upon achievement of certain milestones. Additional milestone payments totaling up to €3.5 million ($4.1 million) in the aggregate are due in connection with the achievement of three commercial milestones, and low single digit royalties are due on aggregate cumulative worldwide net sales of licensed products.At-the-Market OfferingDuring the three and nine months ended September 30, 2020, we issued approximately 5.0 million and 7.2 million shares of common stock at an average price of $3.48 and $3.56 per share for gross proceeds of $17.5 million and $25.6 million, respectively, under the At-the-Market Issuance Sales Agreement (the “Mustang ATM”) with B. Riley FBR, Inc., Cantor Fitzgerald & Co., National Securities Corporation, and Oppenheimer & Co. Inc. (each an "Agent" and collectively, the “Agents”). In connection with these sales, we paid aggregate fees of approximately $0.5 million for net proceeds of approximately $25.1 million.Mustang Public Offering of Common Stock On June 11, 2020, we announced the pricing of an underwritten public offering, whereby we sold 10,769,231 shares of common stock, (plus a 30-day option to purchase up to an additional 1,615,384 shares of common stock, which was partially exercised) at a price of $3.25 per share for gross proceeds of approximately $37.2 million, before deducting underwriting discounts and commissions and offering expenses. In connection with the public offering, the Company paid aggregate fees of approximately $2.2 million for net proceeds of approximately $35.0 million. To date, we have not received approval for the sale of our product candidates in any market and, therefore, have not generated any product sales from our product candidates. In addition, we have incurred substantial operating losses since our inception, and expect to continue to incur significant operating losses for the foreseeable future and may never become profitable. As of September 30, 2020, we have an accumulated deficit of $164.9 million.​We are a majority-controlled subsidiary of Fortress Biotech, Inc. (“Fortress”). As a “Controlled Company” we rely on the exemption provided by Nasdaq Listing Rule 5615(c)(2), which permits us to maintain less than a majority of independent directors on our board.​Critical Accounting Policies and Use of Estimates​See Note 2 to our Financial Statements.​22
| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |
| ​ | ​ | For the three months ended September 30, | ​ | Change |
| ($in thousands) | ​ | 2020 | ​ | 2019 | ​ | $ | ​ | % |
| Operating expenses: | ​ | ​ | ​ | ​ |
| Research and development | ​ | $ | 7,987 | ​ | $ | 7,309 | ​ | $ | 678 | 9 | % |
| Research and development – licenses acquired | ​ | 287 | ​ | 700 | ​ | (413) | (59) | % |
| General and administrative | ​ | 2,153 | ​ | 1,987 | ​ | 166 | 8 | % |
| Total operating expenses | ​ | 10,427 | ​ | 9,996 | ​ | 431 | 4 | % |
| Loss from operations | ​ | (10,427) | ​ | (9,996) | ​ | (431) | 4 | % |
| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |
| Other income (expense) | ​ | ​ | ​ | ​ |
| Interest income | ​ | 162 | ​ | 406 | ​ | (244) | (60) | % |
| Interest expense | ​ | (2,687) | ​ | (578) | ​ | (2,109) | 365 | % |
| Total other income (expense) | ​ | (2,525) | ​ | (172) | ​ | (2,353) | 1,368 | % |
| Net Loss | ​ | $ | (12,952) | ​ | $ | (10,168) | ​ | $ | (2,784) | 27 | % |
| ● | employee-related expenses, which include salaries and benefits; |
| ● | license fees and milestone payments related to in-licensed products and technology; |
| ● | expenses incurred under agreements with contract research organizations, investigative sites and consultants that conduct our clinical trials and our preclinical activities; |
| ● | the cost of acquiring and manufacturing clinical trial materials; and |
| ● | costs associated with non-clinical activities, and regulatory approvals. |

| ● | support of our expanded research and development activities, including additional product candidates entering the clinic under Mustang’s IND; |
| ● | stock compensation granted to key employees and non-employees; |
| ● | support of business development activities; and |
| ● | increased professional fees and other costs associated with the regulatory requirements and increased compliance associated with being a publicly traded company. |
| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |
| ​ | ​ | For the nine months ended September 30, | ​ | Change |
| ($in thousands) | ​ | 2020 | ​ | 2019 | ​ | $ | ​ | % |
| Operating expenses: | ​ | ​ | ​ | ​ |
| Research and development | ​ | $ | 27,131 | ​ | $ | 21,092 | ​ | $ | 6,039 | 29 | % |
| Research and development – licenses acquired | ​ | 1,837 | ​ | 1,350 | ​ | 487 | 36 | % |
| General and administrative | ​ | 7,100 | ​ | 7,520 | ​ | (420) | (6) | % |
| Total operating expenses | ​ | 36,068 | ​ | 29,962 | ​ | 6,106 | 20 | % |
| Loss from operations | ​ | (36,068) | ​ | (29,962) | ​ | (6,106) | 20 | % |
| ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ |
| Other income (expense) | ​ | ​ | ​ | ​ |
| Interest income | ​ | 567 | ​ | 945 | ​ | (378) | (40) | % |
| Interest expense | ​ | (3,906) | ​ | (1,163) | ​ | (2,743) | 236 | % |
| Total other income (expense) | ​ | (3,339) | ​ | (218) | ​ | (3,121) | 1,432 | % |
| Net Loss | ​ | $ | (39,407) | ​ | $ | (30,180) | ​ | $ | (9,227) | 31 | % |

| ● | employee-related expenses, which include salaries and benefits; |
| ● | license fees and milestone payments related to in-licensed products and technology; |
| ● | expenses incurred under agreements with contract research organizations, investigative sites and consultants that conduct our clinical trials and our preclinical activities; |
| ● | the cost of acquiring and manufacturing clinical trial materials; and |
| ● | costs associated with non-clinical activities, and regulatory approvals. |

| ​ | ​ | ​ | ​ | ​ | ​ | ​ |
| ​ | ​ | For the nine months ended September 30, |
| ($in thousands) | ​ | 2020 | ​ | 2019 |
| Statement of cash flows data: | ​ | ​ |
| Total cash (used in) provided by: | ​ | ​ |
| Operating activities | ​ | $ | (27,844) | ​ | $ | (24,091) |
| Investing activities | ​ | (2,948) | ​ | 15,300 |
| Financing activities | ​ | 44,630 | ​ | 65,116 |
| Net change in cash, cash equivalents and restricted cash | ​ | $ | 13,838 | ​ | $ | 56,325 |

​Financing Activities​Net cash provided by financing activities was $44.6 million during the nine months ended September 30, 2020, due to gross proceeds of $37.2 million, net of offering costs of $2.3 million, from our June 2020 underwritten public offering; gross proceeds of $25.6 million, net of offering costs of $0.5 million, from the Mustang ATM; and $0.3 million raised from the issuance of the Company’s common shares in connection with the ESPP, partially offset by the prepayment of the Horizon Notes of $15.8 million.​Net cash provided by financing activities was $65.1 million during the nine months ended September 30, 2019, due to net proceeds of $13.6 million from the Horizon Notes; gross proceeds of $22.5 million, net of offering costs of $0.5 million, from the Mustang ATM; and gross proceeds of $31.6 million, net of offering costs of $2.1 million, from our May 2019 underwritten public offering.​Off-Balance Sheet Arrangements​We are not party to any off-balance sheet transactions. We have no guarantees or obligations other than those which arise out of normal business operations.​
Item 3. Quantitative and Qualitative Disclosures About Market Risks
​
During the three and nine months ended September 30, 2020, there were no material changes to our interest rate risk disclosures, market risk disclosures or foreign currency exchange rate risk disclosures reported in our Annual Report on Form 10-K for the year ended December 31, 2019.
​
Item 4. Controls and Procedures
​
Disclosure Controls and Procedures
​
We maintain “disclosure controls and procedures,” as such term is defined in Rules 13a-15(e) and 15d-15(e) under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), that are designed to ensure that information required to be disclosed by us in reports that we file or submit under the Exchange Act is recorded, processed, summarized, and reported within the time periods specified in Securities and Exchange Commission rules and forms, and that such information is accumulated and communicated to our management, including our Chief Executive Officer and our Principal Financial Officer, to allow timely decisions regarding required disclosure.
​
The design of any disclosure controls and procedures also is based in part upon certain assumptions about the likelihood of future events, and there can be no assurance that any design will succeed in achieving its stated goals under all potential future conditions.
​
With respect to the quarter ended September 30, 2020, under the supervision and with the participation of our management, we conducted an evaluation of the effectiveness of the design and operations of our disclosure controls and procedures. Based upon this evaluation, the Company’s Chief Executive Officer and Principal Financial Officer have concluded that the Company’s disclosure controls and procedures are effective.
​
Management does not expect that our internal control over financial reporting will prevent or detect all errors and all fraud. A control system, no matter how well conceived and operated, can provide only reasonable, not absolute, assurance that the objectives of the control systems are met. Further, the design of a control system must reflect the fact that there are resource constraints, and the benefits of controls must be considered relative to their costs. Because of the inherent limitations in a cost-effective control system, no evaluation of internal control over financial reporting can provide absolute assurance that misstatements due to error or fraud will not occur or that all control issues and instances of fraud, if any, have been or will be detected.
​
27
Changes in Internal Control over Financial Reporting​There were no changes in our internal control over financial reporting (as defined in Rules 13a-15(f) and 15d-15(f) under the Exchange Act) that occurred during the fiscal quarter ended September 30, 2020, which have materially affected, or are reasonably likely to materially affect, our internal control over financial reporting.​​28
PART II. OTHER INFORMATION​
Item 1. Legal Proceedings
​
None
​
Item 1A. Risk Factors
​
The following information sets forth risk factors that could cause our actual results to differ materially from those contained in forward-looking statements we have made in this report and those we may make from time to time. You should carefully consider the risks described below. Our business, financial condition or results of operations could be harmed by any of these risks. The risks and uncertainties described below are not the only ones we face. Additional risks not presently known to us or other factors not perceived by us to present significant risks to our business at this time also may impair our business operations. Additionally, many of these risks and uncertainties are currently elevated by and may or will continue to be elevated by the COVID-19 pandemic.
​
Risks Related to Our Business and Industry
​
Major public health issues, and specifically the pandemic caused by the spread of COVID-19, could have an adverse impact on our financial condition and results of operations and other aspects of our business.
​
In December 2019, a novel strain of coronavirus, COVID-19, was first detected in Wuhan, China, and has since spread around the world. On March 11, 2020, the World Health Organization declared that the rapidly spreading COVID-19 outbreak had evolved into a pandemic. In response to the pandemic, many governments around the world are implementing a variety of measures to reduce the spread of COVID-19, including travel restrictions and bans, instructions to residents to practice social distancing, quarantine advisories, shelter-in-place orders and required closures of non-essential businesses.
​
The COVID-19 pandemic has negatively impacted the global economy, disrupted global supply chains, and created significant volatility and disruption of financial markets. Although COVID-19 has not had a material adverse effect on our business to date, no assurance can be given that it will not in the future if the situation persists or worsens. The extent to which the coronavirus impacts our business and operating results will depend on future developments that are highly uncertain and cannot be accurately predicted, including new information that may emerge concerning the coronavirus and the actions to contain the coronavirus or treat its impact, among others.
​
Should the coronavirus continue to spread, our business operations could be delayed or interrupted. For instance, our clinical trials may be affected by the pandemic. Site initiation, participant recruitment and enrollment, participant dosing, distribution of clinical trial materials, study monitoring and data analysis may be paused or delayed due to changes in hospital or university policies, federal, state or local regulations, prioritization of hospital resources toward pandemic efforts, or other reasons related to the pandemic. If the coronavirus continues to spread, some participants and clinical investigators may not be able to comply with clinical trial protocols. For example, quarantines or other travel limitations (whether voluntary or required) may impede participant movement, affect sponsor access to study sites, or interrupt healthcare services, and we may be unable to conduct our clinical trials. Infections and deaths related to the pandemic may disrupt the United States’ and other countries’ healthcare and healthcare regulatory systems. Such disruptions could divert healthcare resources away from, or materially delay FDA or other regulatory review and/or approval with respect to, our clinical trials. It is unknown how long these disruptions could continue, were they to occur. Any elongation or de-prioritization of our clinical trials or delay in regulatory review resulting from such disruptions could materially affect the development and study of our product candidates.
​
29
| ● | developing our technology platform; |
| ● | identifying, developing, formulating, manufacturing and commercializing product candidates; |

| ● | entering into successful licensing and other arrangements with product development partners; |
| ● | participating in regulatory approval processes, including ultimately gaining approval to market a drug product, which may not occur; |
| ● | obtaining sufficient quantities of our product candidates from our third-party manufacturers to meet clinical trial needs and, if approved, to meet commercial demand at launch and thereafter; |
| ● | establishing and maintaining agreements with wholesalers, distributors and group purchasing organizations on commercially reasonable terms; |
| ● | conducting sales and marketing activities including hiring, training, deploying and supporting our sales force and creating market demand for our product candidates through our own marketing and sales activities, and any other arrangements to promote our product candidates that we may establish; and |
| ● | maintaining patent protection and regulatory exclusivity for our product candidates. |
| ● | obtaining regulatory clearance/approval to commence a clinical trial; |
| ● | identifying, recruiting and training suitable clinical investigators; |
| ● | reaching and preserving agreements on acceptable terms with prospective clinical research organizations (“CROs”) and trial sites, the terms of which can be subject to extensive negotiation, may be subject to modification from time to time and may vary significantly among different CROs and trial sites; |
| ● | obtaining sufficient quantities of a product candidate for use in clinical trials; |
| ● | obtaining Institutional Review Board (“IRB”) or ethics committee approval to conduct a clinical trial at a prospective site; |
| ● | developing and validating companion diagnostics on a timely basis, if required; |

| ● | adding new clinical sites once a trial has begun; |
| ● | change in the principal investigator or other key staff overseeing the clinical trial at a given site; |
| ● | identifying, recruiting and enrolling patients to participate in a clinical trial; or |
| ● | retaining (or replacing) patients who have initiated a clinical trial but who may withdraw due to adverse events from the therapy, insufficient efficacy, fatigue with the clinical trial process, personal issues, or other reasons. |
| ● | failure to conduct the clinical trial in accordance with regulatory requirements or our clinical protocols; |
| ● | inspection of the clinical trial operations or clinical trial site by the FDA or other regulatory authorities resulting in the imposition of a clinical hold; |
| ● | stopping rules contained in the protocol; |
| ● | unforeseen safety issues or any determination that the clinical trial presents unacceptable health risks; and |
| ● | lack of adequate funding to continue the clinical trial. |

| ● | the FDA or comparable foreign regulatory authorities may disagree with the design or implementation of our clinical trials; |
| ● | our inability to demonstrate to the satisfaction of the FDA that a product candidate is safe and effective for an indication; |
| ● | the FDA may not accept clinical data from trials conducted by individual investigators or in countries where the standard of care is potentially different from that of the United States; |
| ● | the results of clinical trials may not meet the level of statistical significance required by the FDA for approval; |
| ● | the FDA may disagree with the interpretation of data from preclinical studies or clinical trials; |
| ● | the FDA may not approve the manufacturing processes or facilities or those of third-party manufacturers with which we or our respective collaborators currently contract for clinical supplies and plan to contract for commercial supplies; or |
| ● | the approval policies or regulations of the FDA may significantly change in a manner rendering the clinical data insufficient for approval or the product characteristics or benefit-risk profile unfavorable for approval. |

With respect to foreign markets, approval procedures vary among countries and, in addition to the aforementioned risks, can involve additional product testing, administrative review periods and agreements with pricing authorities. In addition, recent events raising questions about the safety of certain marketed pharmaceuticals may result in increased cautiousness by the FDA and comparable foreign regulatory authorities in reviewing new pharmaceuticals based on safety, efficacy or other regulatory considerations and may result in significant delays in obtaining regulatory approvals. Any delay in obtaining, or inability to obtain, applicable regulatory approvals would prevent us from commercializing our product candidates.​Any product candidate we advance into clinical trials may cause unacceptable adverse events or have other properties that may delay or prevent their regulatory approval or commercialization or limit their commercial potential.​Unacceptable adverse events caused by any of our product candidates that we advance into clinical trials could cause regulatory authorities to interrupt, delay or stop clinical trials and could result in the denial of regulatory approval by the FDA or other regulatory authorities for any or all targeted indications and markets. This, in turn, could prevent us from commercializing the affected product candidate and generating revenues from its sale.​We have not completed testing for any of our product candidates for the indications for which we intend to seek product approval in humans, and we currently do not know the extent of the adverse events, if any, that will be observed in patients who receive any of our product candidates. If any of our product candidates causes unacceptable adverse events in clinical trials, we may not be able to obtain regulatory approval or commercialize such products, or, if such product candidates are approved for marketing, future adverse events could cause us to withdraw such products from the market.​If any of our product candidates is approved and we or our contract manufacturer(s) fail to produce the product, or components of the product, in the volumes that we require on a timely basis, or fail to comply with stringent regulations applicable to pharmaceutical drug manufacturers, we may face delays in the commercialization of our product candidates or be unable to meet market demand, and may lose potential revenues.​The manufacture of pharmaceutical products requires significant expertise and capital investment, including the development of advanced manufacturing techniques and process controls, and the use of specialized processing equipment. We may enter into development and supply agreements with contract manufacturers for the completion of pre-commercialization manufacturing development activities and, if approved, the manufacture of commercial supplies for one or more of our product candidates. Any termination or disruption of our relationships with our contract manufacturers may materially harm our business and financial condition and frustrate any commercialization efforts for each respective product candidate.​All of our contract manufacturers must comply with strictly enforced federal, state and foreign regulations, including current good manufacturing practice (“cGMP”) requirements enforced by the FDA through its establishment inspection program. We are required by law to establish adequate oversight and control over raw materials, components and finished products furnished by our third-party suppliers and contract manufacturers, but we have little control over their compliance with these regulations. Any failure to comply with applicable regulations may result in fines and civil penalties, suspension of production, restrictions on imports and exports, suspension or delay in product approval, product seizure or recall, or withdrawal of product approval, and would limit the availability of our product and customer confidence in our product. Any manufacturing defect or error discovered after products have been produced and distributed could result in even more significant consequences, including costly recalls, re-stocking costs, damage to our reputation and potential for product liability claims.​If the contract manufacturers upon whom we may rely to manufacture one or more of our product candidates, and any future product candidate we may in-license, fail to deliver the required commercial quantities on a timely basis at commercially reasonable prices, we would likely be unable to meet demand for our products and we would lose potential revenues.​34
We rely on third parties to conduct all aspects of our lentiviral vector production and these third parties may not perform satisfactorily.​We do not independently conduct our lentiviral vector production and we currently rely, and expect to continue to rely, on third parties with respect to the manufacture of these items.​Our reliance on these third parties for manufacturing lentiviral vector reduces our control over these activities but will not relieve us of our responsibility to ensure compliance with all required regulations and study protocols. For products that we develop and commercialize, we will remain responsible for ensuring that each of our IND-enabling studies and clinical studies is conducted in accordance with the study plan and protocols, and that our lentiviral vectors are manufactured in accordance with GMP as applied in the relevant jurisdictions.​If these third parties do not successfully carry out their contractual duties, meet expected deadlines, conduct our studies in accordance with regulatory requirements or our stated study plans and protocols, or manufacture our lentiviral vectors in accordance with GMP, we will not be able to complete, or may be delayed in completing, the preclinical and clinical studies and manufacturing process validation activities required to support future IND, market authorization application and BLA submissions and approval of our product candidates, or to support commercialization of our products, if approved. Many of our agreements with these third parties contain termination provisions that allow these third parties to terminate their relationships with us at any time. If we need to enter into alternative arrangements, our product development and commercialization activities could be delayed.​We may be forced to enter into an agreement with a different manufacturer, which we may not be able to do on reasonable terms, if at all. In some cases, the technical skills required to manufacture lentiviral vector for our drug product candidates may be unique or proprietary to the original manufacturer, and we may have difficulty or there may be contractual restrictions prohibiting us from, transferring such skills to a back-up or alternate supplier, or we may be unable to transfer such skills at all. Any of these events could lead to clinical study delays or failure to obtain marketing approval or impact our ability to successfully commercialize our product or any future products. Some of these events could be the basis for FDA action, including injunction, recall, seizure or total or partial suspension of production.​Our approach to the development of our product candidates is unproven, and we do not know whether we will be able to develop any products of commercial value.​Our products candidates are emerging technologies and, consequently, it is conceivable that such technologies may ultimately fail to develop into commercially viable therapies to treat human patients with cancer or other diseases. One of the reasons for the lack of commercial viability could be our inability to obtain regulatory approval for such technologies.​35
| ● | regulatory authorities may require the addition of unfavorable labeling statements, including specific warnings, black box warnings, adverse reactions, precautions, and/or contraindications; |
| ● | regulatory authorities may suspend or withdraw their approval of the product, and/or require it to be removed from the market; |
| ● | we may be required to change the way the product is administered, conduct additional clinical trials or change the labeling of the product; or |
| ● | our reputation may suffer. |

| ● | restrictions on such products, operations, manufacturers or manufacturing processes; |
| ● | restrictions on the labeling or marketing of a product; |
| ● | restrictions on product distribution or use; |
| ● | requirements to conduct post-marketing studies or clinical trials; |
| ● | warning letters, untitled letters, import alerts, and/or inspection observations; |
| ● | withdrawal of the products from the market; |
| ● | refusal to approve pending applications or supplements to approved applications that we submit; |
| ● | recall of products; |
| ● | fines, restitution or disgorgement of profits; |
| ● | suspension or withdrawal of marketing or regulatory approvals; |
| ● | suspension of any ongoing clinical trials; |
| ● | refusal to permit the import or export of our products; |
| ● | product seizure; or |
| ● | injunctions, consent decrees, and/or the imposition of civil or criminal penalties. |

| ● | the federal Anti-Kickback Statute, which prohibits, among other things, persons from knowingly and willfully soliciting, offering, receiving or providing remuneration, directly or indirectly, in cash or in kind, to induce or reward, or in return for, either the referral of an individual for, or the purchase, order or recommendation of, any good or service, for which payment may be made under federal and state healthcare programs, such as Medicare and Medicaid; |
| ● | federal civil and criminal false claims laws and civil monetary penalty laws, including the federal False Claims Act, which impose criminal and civil penalties, including civil whistleblower or qui tam actions, against individuals or entities for knowingly presenting, or causing to be presented, to the federal government, including the Medicare and Medicaid programs, claims for payment that are false or fraudulent or making a false statement to avoid, decrease or conceal an obligation to pay money to the federal government; the federal Health Insurance Portability and Accountability Act of 1996 (“HIPAA”), which imposes criminal and civil liability for executing a scheme to defraud any healthcare benefit program or making false statements relating to healthcare matters; |
| ● | HIPAA, as amended by the Health Information Technology for Economic and Clinical Health Act of 2009 (“HITECH”), and their respective implementing regulations, which impose obligations on covered healthcare providers, health plans, and healthcare clearinghouses, as well as their business associates that create, receive, maintain or transmit individually identifiable health information for or on behalf of a covered entity, with respect to safeguarding the privacy, security and transmission of individually identifiable health information; |

| ● | the federal Open Payments program, which requires manufacturers of certain approved drugs, devices, biologics and medical supplies for which payment is available under Medicare, Medicaid or the Children’s Health Insurance Program, with specific exceptions, to report annually to the Centers for Medicare & Medicaid Services (“CMS”), information related to “payments or other transfers of value” made to physicians, which is defined to include doctors, dentists, optometrists, podiatrists and chiropractors, and teaching hospitals and applicable manufacturers and applicable group purchasing organizations to report annually to CMS ownership and investment interests held by the physicians and their immediate family members. Data collection began on August 1, 2013, with requirements for manufacturers to submit reports to CMS by March 31, 2014, and 90 days after the end each subsequent calendar year. Disclosure of such information was made by CMS on a publicly available website beginning in September 2014 and is annually updated; and |
| ● | analogous state and foreign laws and regulations, such as state anti-kickback and false claims laws, which may apply to sales or marketing arrangements and claims involving healthcare items or services reimbursed by non-governmental third-party payors, including private insurers; state and foreign laws that require pharmaceutical companies to comply with the pharmaceutical industry’s voluntary compliance guidelines and the relevant compliance guidance promulgated by the federal government or otherwise restrict payments that may be made to healthcare providers; state and foreign laws that require drug manufacturers to report information related to payments and other transfers of value to physicians and other healthcare providers or marketing expenditures; and state and foreign laws governing the privacy and security of health information in certain circumstances, many of which differ from each other in significant ways and often are not preempted by HIPAA, thus complicating compliance efforts. |

| ● | an annual, nondeductible fee on any entity that manufactures, or imports specified branded prescription drugs and biologic agents, apportioned among these entities according to their market share in certain government healthcare programs; |
| ● | an increase in the statutory minimum rebates a manufacturer must pay under the Medicaid Drug Rebate Program to 23.1% and 13.0% of the average manufacturer price for branded and generic drugs, respectively; |
| ● | expansion of healthcare fraud and abuse laws, including the federal False Claims Act and the federal Anti-Kickback Statute, new government investigative powers and enhanced penalties for non-compliance; |
| ● | a new Medicare Part D coverage gap discount program, in which manufacturers must agree to offer point-of-sale discounts off negotiated prices of applicable brand drugs to eligible beneficiaries during their coverage gap period, as a condition for a manufacturer’s outpatient drugs to be covered under Medicare Part D; |
| ● | extension of a manufacturer’s Medicaid rebate liability to covered drugs dispensed to individuals who are enrolled in Medicaid managed care organizations; |

| ● | expansion of eligibility criteria for Medicaid programs by, among other things, allowing states to offer Medicaid coverage to additional individuals and by adding new mandatory eligibility categories for certain individuals with income at or below 138% of the federal poverty level, thereby potentially increasing a manufacturer’s Medicaid rebate liability; |
| ● | expansion of the entities eligible to enroll in the 340B Drug Pricing Program to include certain critical access hospitals, freestanding cancer hospitals, rural referral centers, and sole community hospitals, but exempting certain drugs from the ceiling price requirements for these covered entities; |
| ● | the new requirements under the federal Open Payments program and its implementing regulations; |
| ● | a new requirement to annually report drug samples that manufacturers and distributors provide to physicians; |
| ● | a new regulatory pathway for the approval of biosimilar biological products, all of which will impact existing government healthcare programs and will result in the development of new programs; and |
| ● | a new Patient-Centered Outcomes Research Institute to oversee, identify priorities in, and conduct comparative clinical effectiveness research, along with funding for such research. |

HHS has made numerous other proposals aimed at lowering drug prices for Medicare beneficiaries and increasing price transparency. These proposals include giving Medicare Advantage and Part D plans flexibility in the availability of drugs in “protected classes,” more transparency in the cost of drugs, including the beneficiary’s financial liability, and less costly alternatives and permitting the use of step therapy as a means of prior authorization. HHS has also proposed requiring pharmaceutical manufacturers disclose the prices of certain drugs in direct-to-consumer television advertisements. The proposal related to protected classes has been withdrawn and the disclosure requirements have been rejected by the courts. In addition, a proposed rule that would have passed drug rebates to consumers at the point of sale also has been withdrawn. However, it appears the Trump Administration will continue to explore its authority to make regulatory changes to the pharmaceutical industry. For example, the Trump Administration released an Advance Notice of Proposed Rulemaking related to an international price index model. It is unclear what eventually will be proposed, but the President has alluded to the concept of “most favored nation” pricing with regards to U.S. drug purchasing. In addition, HHS, in conjunction with the FDA, released two pharmaceutical importation models in December 2019: (1) a Notice of Proposed Rulemaking to permit importation of pharmaceuticals from Canada, and (2) draft FDA guidance permitting manufacturers to import their own pharmaceuticals that were originally intended for marketing in other countries.​HHS also has taken steps to increase the availability of cheaper health insurance options, typically with fewer benefits and less generous coverage. The Administration has also signaled its intention to address drug prices and to increase competition, including by increasing the availability of biosimilars and generic drugs. As these are regulatory actions, a new administration could undo or modify these efforts.​We expect that the ACA, as well as other healthcare reform measures that may be adopted in the future, may result in more rigorous coverage criteria and in additional downward pressure on the price that we receive for any approved drug. Any reduction in reimbursement from Medicare or other government healthcare programs may result in a similar reduction in payments from private payors. The implementation of cost containment measures or other healthcare reforms may prevent us from being able to generate revenue, attain profitability or commercialize our drugs.​Legislative proposals such as expanding the Medicaid drug rebate program to the Medicare Part D program, providing authority for the government to negotiate drug prices under the Medicare Part D program and lowering reimbursement for drugs covered under the Medicare Part B program have been raised in Congress, but have been met with opposition and have not been enacted so far.​The administration can rely on its existing statutory authority to make policy changes that could have an impact on the drug industry. For example, the Medicare program has in the past proposed to test alternative payment methodologies for drugs covered under the Part B program and currently is proposing to pay hospitals less for Part B-covered drugs purchased through the 340B Drug Pricing Program.​Legislative and regulatory proposals have been made to expand post-approval requirements and restrict sales and promotional activities for drugs. We cannot be sure whether additional legislative changes will be enacted, or whether the FDA regulations, guidance or interpretations will be changed, or what the impact of such changes on the marketing approvals of our product candidates, if any, may be. In addition, increased scrutiny by the U.S. Congress of the FDA’s approval process may significantly delay or prevent marketing approval, as well as subject us to more stringent product labeling and post-marketing testing and other requirements.​​​Most recently, in July 2020, President Trump signed four Executive Orders directing HHS to take several steps to lower costs on prescription drugs. Many of the policy changes included in the Executive Orders were proposed in President Trump’s May 2018 Blueprint to Lower Drug Prices and Reduce Out-of-Pocket Costs. The Executive Orders cover a range of policies, including but not limited to (i) tying the prices paid by the U.S. government (e.g., Medicare) for drugs and biological products to prices paid in other countries; (ii) ensuring that rebates that drug makers pay to pharmacy benefit managers and insurers in the Medicare Part D program get passed directly to patients when they purchase a medication, so long as the change is not projected to increase Federal spending, Medicare beneficiary premiums or patients’ total out-of-pocket costs; and (iii) allowing states, wholesalers and pharmacies to import FDA-approved drugs from Canada and other countries and sell them in the U.S. if the FDA deems them safe. Many of these policy proposals have been considered 42
| ● | On October 9, 2019, CMS issued a proposed rule entitled, Modernizing and Clarifying the Physician Self-Referral Regulations and on the same day the HHS Office of Inspector General issued a similar rule, entitled Revisions to Safe Harbors Under the Anti-Kickback Statute, and Civil Monetary penalty Rules Regarding Beneficiary Inducements. The proposed rules are an effort to reform regulations dealing with anti-kickback and self-referral laws. The proposals are attempting to allow certain financial arrangements that would otherwise violate anti-kickback and self-referral laws for providers that are participating in value-based payment arrangements. The proposed rule could impact drug purchasing behavior to ensure providers are within their budget and/or restructure existing payment structures between providers and manufacturers. |
| ● | On October 30, 2019, the Administration issued an advanced notice of proposed rulemaking (“ANPRM”) entitled, International Pricing Index Model for Medicare Part B Drugs. This ANPRM is soliciting feedback on a potential proposal to align United States drug prices in the Medicare Part B program with international prices. It also solicits public feedback on a policy that would allowing private-sector vendors to negotiate prices, take title to drugs, and improve competition for hospital and physician business. Although this is only a notice for a potential rule, it signals the Administration’s desire to regulatorily influence the United States drug pricing system that could adversely affect the industry. |
| ● | On November 15, 2019, CMS issued a proposed rule entitled, Transparency in Coverage and finalized the Calendar Year (“CY”) 2020 Outpatient Prospective Payment System (“OPPS”) & Ambulatory Surgical Center Price Transparency Requirements for Hospitals to Make Standard Charges Rule. Together the rules would increase price transparency through health plans and in hospitals. The affects may influence consumer purchasing habits in the health care sector as a whole. Although the transparency provisions are not yet in effect and the hospital price transparency requirements are subject to litigation, there could be implications for the industry related to drug pricing if or when it is enacted. |
| ● | On November 18, 2019, CMS issued a proposed rule entitled, Medicaid Fiscal Accountability Regulation (“MFAR”). The proposed rule would significantly impact states’ ability to finance their Medicaid programs. If finalized, the MFAR could force states to restructure their Medicaid financing that could disincentivize or change state prescription drug purchasing behavior that would adversely impact the industry. |
| ● | On December 18, 2019, the FDA issued a proposed rule entitled, Importation of Prescription Drugs. The proposed rule would allow the importation of certain prescription drugs from Canada. If finalized, states or other non-federal government entities would be able to submit importation program proposals to FDA for review and authorization. This proposed rule could also influence pricing practices in the United States. |

| ● | On January 30, 2020, CMS issued a state waiver option entitled, Health Adult Opportunity (“HAO”). The HAO would allow states to restructure benefits and coverage policies for their Medicaid programs. The HAO will provide states administrative flexibilities in exchange for a capped federal share. The cap on the federal share is commonly referred to as a “block grant.” Importantly, the HAO allows states to set formularies that align with Essential Health Benefit requirements while still requiring manufacturers to participate in the Medicaid Rebate Program. Depending on utilization of the HAO by states, it could impact the industry – especially if states elect to use a formulary. |

| ● | the severity of the disease under investigation; |
| ● | the eligibility criteria for the study in question; |
| ● | the perceived risks and benefits of the product candidate under study; |
| ● | the efforts to facilitate timely enrollment in clinical trials; |
| ● | the patient referral practices of physicians; |
| ● | the number of clinical trials sponsored by other companies for the same patient population; |
| ● | the ability to monitor patients adequately during and after treatment; and |
| ● | the proximity and availability of clinical trial sites for prospective patients. |
| ● | capital resources; |

| ● | development resources, including personnel and technology; |
| ● | clinical trial experience; |
| ● | regulatory experience; |
| ● | expertise in prosecution of intellectual property rights; and |
| ● | manufacturing, distribution and sales and marketing experience. |
| ● | the efficacy and safety as demonstrated in clinical trials; |
| ● | the timing of market introduction of such product candidate as well as competitive products; |
| ● | the clinical indications for which the drug is approved; |
| ● | acceptance by physicians, major operators of cancer clinics and patients of the drug as a safe and effective treatment; |
| ● | the safety of such product candidates seen in a broader patient group (i.e., based on actual use); |
| ● | the availability, cost and potential advantages of alternative treatments, including less expensive generic drugs; |
| ● | the availability of adequate reimbursement and pricing by third-party payors and government authorities; |
| ● | changes in regulatory requirements by government authorities for our product candidates; |
| ● | the relative convenience and ease of administration of the product candidate for clinical practices; |
| ● | the product labeling or product insert required by the FDA or regulatory authority in other countries; |
| ● | the approval, availability, market acceptance and reimbursement for a companion diagnostic, if any; |
| ● | the prevalence and severity of adverse side effects; and |
| ● | the effectiveness of our sales and marketing efforts. |

If any product candidate that we develop does not provide a treatment regimen that is as beneficial as, or is not perceived as being as beneficial as, the current standard of care or otherwise does not provide patient benefit, that product candidate, if approved for commercial sale by the FDA or other regulatory authorities, likely will not achieve market acceptance. Our ability to effectively promote and sell any approved products will also depend on pricing and cost-effectiveness, including our ability to produce a product at a competitive price and our ability to obtain sufficient third-party coverage or reimbursement. If any product candidate is approved but does not achieve an adequate level of acceptance by physicians, patients and third-party payors, our ability to generate revenues from that product would be substantially reduced. In addition, our efforts to educate the medical community and third-party payors on the benefits of our product candidates may require significant resources, may be constrained by FDA rules and policies on product promotion, and may never be successful.​If approved, our product candidates will face competition from less expensive generic products of competitors, and, if we are unable to differentiate the benefits of our product candidates over these less expensive alternatives, we may never generate meaningful product revenues.​Generic therapies are typically sold at lower prices than branded therapies and are generally preferred by hospital formularies and managed care providers of health services. We anticipate that, if approved, our product candidates will face increasing competition in the form of generic versions of branded products of competitors, including those that have lost or will lose their patent exclusivity. In the future, we may face additional competition from a generic form when the patents covering them begin to expire, or earlier if the patents are successfully challenged. If we are unable to demonstrate to physicians and payers that the key differentiating features of our product candidates translate to overall clinical benefit or lower cost of care, we may not be able to compete with generic alternatives.​Reimbursement may be limited or unavailable in certain market segments for our product candidates, which could make it difficult for us to sell our products profitably.​There is significant uncertainty related to the third-party coverage and reimbursement of newly approved drugs. Such third-party payors include government health programs such as Medicare, managed care providers, private health insurers and other organizations. We intend to seek approval to market our product candidates in the U.S., the EU and other selected foreign jurisdictions. Market acceptance and sales of our product candidates in both domestic and international markets will depend significantly on the availability of adequate coverage and reimbursement from third-party payors for any of our product candidates and may be affected by existing and future health care reform measures. Government and other third-party payors are increasingly attempting to contain healthcare costs by limiting both coverage and the level of reimbursement for new drugs and, as a result, they may not cover or provide adequate payment for our product candidates. These payors may conclude that our product candidates are less safe, less effective or less cost-effective than existing or future introduced products, and third-party payors may not approve our product candidates for coverage and reimbursement or may cease providing coverage and reimbursement for these product candidates.​Obtaining coverage and reimbursement approval for a product from a government or other third-party payor is a time consuming and costly process that could require us to provide to the payor supporting scientific, clinical and cost-effectiveness data for the use of our products. We may not be able to provide data sufficient to gain acceptance with respect to coverage and reimbursement. If reimbursement of our future products is unavailable or limited in scope or amount, or if pricing is set at unsatisfactory levels, we may be unable to achieve or sustain profitability.​In some foreign countries, particularly in the EU, the pricing of prescription pharmaceuticals is subject to governmental control. In these countries, pricing negotiations with governmental authorities can take considerable time after the receipt of marketing approval for a product candidate. To obtain reimbursement or pricing approval in some countries, we may be required to conduct additional clinical trials that compare the cost-effectiveness of our product candidates to other available therapies. If reimbursement of our product candidates is unavailable or limited in scope or amount in a particular country, or if pricing is set at unsatisfactory levels, we may be unable to achieve or sustain profitability of our products in such country.​47
| ● | our inability to recruit, train and retain adequate numbers of effective sales and marketing personnel; |
| ● | the inability of sales personnel to obtain access to physicians or persuade adequate numbers of physicians to prescribe any future products; |
| ● | the lack of complementary or other products to be offered by sales personnel, which may put us at a competitive disadvantage from the perspective of sales efficiency relative to companies with more extensive product lines; and |
| ● | unforeseen costs and expenses associated with creating our own sales and marketing organization. |

Our reliance on these third parties for research and development activities reduces our control over these activities but does not relieve us of our responsibilities. For example, we remain responsible for ensuring that each of our preclinical studies and clinical trials are conducted in accordance with the general investigational plan and protocols for the trial and for ensuring that our preclinical studies are conducted in accordance with good laboratory practices (“GLPs”) as appropriate. Moreover, the FDA requires us to comply with standards, commonly referred to as good clinical practices (“GCPs”) for conducting, recording and reporting the results of clinical trials to assure that data and reported results are credible and accurate and that the rights, integrity and confidentiality of trial participants are protected. Regulatory authorities enforce these requirements through periodic inspections of trial sponsors, clinical investigators and trial sites. If we or any of our CROs fail to comply with applicable GCPs, the clinical data generated in our clinical trials may be deemed unreliable and the FDA or comparable foreign regulatory authorities may require us to perform additional clinical trials before approving our marketing applications. We cannot assure you that upon inspection by a regulatory authority, such regulatory authority will determine that any of our clinical trials complies with GCP regulations. In addition, our clinical trials must be conducted with product produced under cGMP regulations. Our failure to comply with these regulations may require us to repeat clinical trials, which would delay the regulatory approval process. We also are required to register ongoing clinical trials and post the results of completed clinical trials on a government-sponsored database, ClinicalTrials.gov, within specified timeframes. Failure to do so can result in fines, adverse publicity and civil and criminal sanctions.​The third parties with whom we have contracted to help perform our preclinical studies and/or clinical trials may also have relationships with other entities, some of which may be our competitors. If these third parties do not successfully carry out their contractual duties, meet expected deadlines or conduct our preclinical studies or clinical trials in accordance with regulatory requirements or our stated protocols, we will not be able to obtain, or may be delayed in obtaining, marketing approvals for our product candidates and will not be able to, or may be delayed in our efforts to, successfully commercialize our product candidates.​If any of our relationships with these third-party contract research organizations or site management organizations terminates, we may not be able to enter into arrangements with alternative contract research organizations or site management organizations or to do so on commercially reasonable terms. Switching or adding additional contract research organizations or site management organizations involves additional cost and requires management time and focus. In addition, there is a natural transition period when a new contract research organization or site management organization commences work. As a result, delays could occur, which could compromise our ability to meet our desired development timelines. Though we carefully manage our relationships with our contract research organizations or site management organizations, there can be no assurance that we will not encounter similar challenges or delays in the future. Forces beyond our control, including the impacts of COVID-19, could disrupt the ability of our third-party CROs, site management organizations, clinical data management organizations, medical institutions, and clinical investigators to conduct our preclinical studies and our clinical trials for our product candidates and for any future product candidate. For instance, the developing situation in China and globally regarding the coronavirus disease outbreak has the potential to adversely impact our product development activities. At this time, the impact of the coronavirus disease outbreak is not having a material adverse effect on our business, but no assurance can be given it will not in the future if the situation persists.​We contract with third parties for the manufacture of our product candidates for preclinical and clinical testing and may also do so for commercialization, if and when our product candidates are approved. This reliance on third parties increases the risk that we will not have sufficient quantities of our product candidates or any future product candidate or such quantities at an acceptable cost, which could delay, prevent or impair our development or commercialization efforts.​We may rely on third-party manufacturers or third-party collaborators for the manufacture of commercial supply of one or more product candidates for which our collaborators or we obtain marketing approval. We may be unable to establish any agreements with third-party manufacturers or to do so on acceptable terms. Even if we are able to establish agreements with third-party manufacturers, reliance on third-party manufacturers entails additional risks, including, but not necessarily limited to:49
| ● | reliance on the third party for regulatory compliance and quality assurance, while still being required by law to establish adequate oversight and control over products furnished by that third party; |
| ● | the possible breach of the manufacturing agreement by the third party; |
| ● | manufacturing delays if our third-party manufacturers are unable to obtain raw materials due to supply chain disruptions, give greater priority to the supply of other products over our product candidates or otherwise do not satisfactorily perform according to the terms of the agreement between us; |
| ● | the possible misappropriation of our proprietary information, including our trade secrets and know-how; and |
| ● | the possible termination or nonrenewal of the agreement by the third party at a time that is costly or inconvenient for us. |

Future dependence upon others for the manufacture of our product candidates or products may adversely affect our future profit margins and our ability to commercialize any products that may receive marketing approval on a timely and competitive basis.​We also expect to rely on other third parties to distribute drug supplies for our clinical trials. Any performance failure on the part of our distributors could delay clinical development or marketing approval of our product candidates or commercialization of our products, if approved, producing additional losses and depriving us of potential product revenue.​We rely on clinical data and results obtained by third parties that could ultimately prove to be inaccurate or unreliable.​As part of our strategy to mitigate development risk, we seek to develop product candidates with well-studied mechanisms of action, and we utilize biomarkers to assess potential clinical efficacy early in the development process. This strategy necessarily relies upon clinical data and other results obtained by third parties that may ultimately prove to be inaccurate or unreliable. Further, such clinical data and results may be based on products or product candidates that are significantly different from our product candidates or any future product candidate. If the third-party data and results we rely upon prove to be inaccurate, unreliable or not applicable to our product candidates or future product candidate, we could make inaccurate assumptions and conclusions about our product candidates and our research and development efforts could be compromised.​If we breach any of the agreements under which we license rights to one or more of product candidates from others, we could lose the ability to continue to develop and, if approved, commercialize such product candidate.​Because we have in-licensed the rights to all of our product candidates from COH, Fred Hutch, St. Jude and Nationwide, and in the future will continue to in-license from additional third parties, if there is any dispute between us and our licensor regarding our rights under our license agreement, our ability to develop and commercialize these product candidates may be adversely affected. Any uncured, material breach under our license agreement could result in our loss of exclusive rights to our product candidate and may lead to a complete termination of our related product development efforts.​We may not be able to manage our business effectively if we are unable to attract and retain key personnel.​We may not be able to attract or retain qualified management and commercial, scientific and clinical personnel in the future due to the intense competition for qualified personnel among biotechnology, pharmaceutical and other businesses. If we are not able to attract and retain necessary personnel to accomplish our business objectives, we may experience constraints that will significantly impede the achievement of our development objectives, our ability to raise additional capital and our ability to implement our business strategy.​51
| ● | withdrawal of clinical trial participants; |
| ● | suspension or termination of clinical trial sites or entire trial programs; |
| ● | decreased demand for any product candidates or products that we may develop; |
| ● | initiation of investigations by regulators; |
| ● | impairment of our business reputation; |

| ● | costs of related litigation; |
| ● | substantial monetary awards to patients or other claimants; |
| ● | loss of revenues; |
| ● | reduced resources of our management to pursue our business strategy; and |
| ● | the inability to commercialize our product candidate or future product candidates. |
| ● | exposure to unknown liabilities; |
| ● | disruption of our business and diversion of our management’s time and attention to develop acquired products or technologies; |
| ● | difficulty or inability to secure financing to fund development activities for such acquired or in-licensed technologies in the current economic environment; |
| ● | incurrence of substantial debt or dilutive issuances of securities to pay for acquisitions; |
| ● | higher than expected acquisition and integration costs; |
| ● | increased amortization expenses; |
| ● | difficulty and cost in combining the operations and personnel of any acquired businesses with our operations and personnel; |
| ● | impairment of relationships with key suppliers or customers of any acquired businesses due to changes in management and ownership; and |

| ● | inability to retain key employees of any acquired businesses. |

| ● | human error; |
| ● | subsystem, component, or software failure; |
| ● | a power or telecommunications failure; |
| ● | hacker attacks, cyber-attacks, software viruses, security breaches, unauthorized access or intentional acts of vandalism; or |
| ● | terrorist acts or war. |

| ● | obtaining regulatory approval from the FDA and other regulatory authorities that may have very limited experience with the commercial development of genetically modified T cell therapies for cancer; |
| ● | developing and deploying consistent and reliable processes for engineering a patient’s T cells ex vivo and infusing the engineered T cells back into the patient; |
| ● | conditioning patients with chemotherapy in conjunction with delivering each of our products, which may increase the risk of adverse side effects of our products; |
| ● | educating medical personnel regarding the potential side effect profile of each of our products; |
| ● | developing processes for the safe administration of these products, including long-term follow-up for all patients who receive our product candidates; |
| ● | sourcing clinical and, if approved, commercial supplies for the materials used to manufacture and process our product candidates; |
| ● | developing a manufacturing process and distribution network with a cost of goods that allows for an attractive return on investment; |
| ● | establishing sales and marketing capabilities after obtaining any regulatory approval to gain market acceptance, and obtaining adequate coverage, reimbursement, and pricing by third-party payors and government authorities; and |
| ● | developing therapies for types of cancers beyond those addressed by our current product candidates. |

Product candidates, even if successfully developed and commercialized, may be effective only in combating certain specific types of cancer, and the market for drugs designed to combat such cancer type(s) may be small and unprofitable.​There are many different types of cancer, and a treatment that is effective against one type of cancer may not be effective against another. CAR T or other technologies we pursue may only be effective in combating specific types of cancer but not others. Even if one or more of our products proves to be an effective treatment against a given type of cancer, the number of patients suffering from such cancer may be small, in which case potential sales from a therapy designed to combat such cancer would be limited.​Our gene therapy product candidates are based on a novel technology, which makes it difficult to predict the time and cost of product candidate development and subsequently obtaining regulatory approval.​We have concentrated a portion of our therapeutic product research and development efforts on our gene therapy platform, and our future success depends, in part, on the successful development of this therapeutic approach. There can be no assurance that any development problems we experience in the future related to our gene therapy platform will not cause significant delays or unanticipated costs, or that such development problems can be solved. We may also experience delays in developing a sustainable, reproducible and commercial-scale manufacturing process or transferring that process to commercial partners, which may prevent us from completing our clinical studies or commercializing our products on a timely or profitable basis, if at all.​In addition, the clinical study requirements of the FDA, the European Medicines Agency, or EMA, and other regulatory agencies and the criteria these regulators use to determine the safety and efficacy of a product candidate vary substantially according to the type, complexity, novelty and intended use and market of the potential products. The regulatory approval process for novel product candidates such as ours can be more expensive and take longer than for other, better known or more extensively studied pharmaceutical or other product candidates. Currently, a limited number of gene therapy products, including CAR T therapies, have been approved by the FDA, the EMA and the European Commission. Given the few precedents of approved gene therapy products, it is difficult to determine how long it will take or how much it will cost to obtain regulatory approvals for our product candidates in the United States, the EU or other jurisdictions. Approvals by the EMA and the European Commission may not be indicative of what the FDA may require for approval.​Regulatory requirements governing the development of gene therapy products have changed frequently and may continue to change in the future. The FDA has established the Office of Tissues and Advanced Therapies within the Center for Biologics Evaluation and Research, or CBER, to consolidate the review of gene therapy and related products, and to advise the CBER on its review. The FDA can put an investigational new drug application, or IND, on clinical hold if the information in an IND is not sufficient to assess the risks in pediatric patients. Before a clinical study can begin at any institution, that institution’s IRB and its Institutional Biosafety Committee will have to review the proposed clinical study to assess the safety of the study. Moreover, serious adverse events or developments in clinical trials of gene therapy product candidates conducted by others may cause the FDA or other regulatory bodies to initiate a clinical hold on our clinical trials or otherwise change the requirements for approval of any of our product candidates.​These regulatory review agencies, committees and advisory groups and the new requirements and guidelines they promulgate may lengthen the regulatory review process, require us to perform additional or larger studies, increase our development costs, lead to changes in regulatory positions and interpretations, delay or prevent approval and commercialization of these treatment candidates or lead to significant post-approval studies, limitations or restrictions. As we advance our product candidates, we will be required to consult with these regulatory and advisory groups and comply with applicable requirements and guidelines. If we fail to do so, we may be required to delay or discontinue development of our product candidates. Delay or failure to obtain, or unexpected costs in obtaining, the regulatory approval necessary to bring a potential product to market could decrease our ability to generate sufficient product revenue to maintain our business.​57
| ● | patent applications may not result in any patents being issued, or the scope of issued patents may not extend to competitive product candidates and their formulations and uses developed or produced by others; |
| ● | our competitors, many of which have substantially greater resources than us or our partners, and many of which have made significant investments in competing technologies, may seek, or may already have obtained, patents that may limit or interfere with our abilities to make, use, and sell potential product candidates, file new patent applications, or may affect any pending patent applications that we may have; |

| ● | there may be significant pressure on the U.S. government and other international governmental bodies to limit the scope of patent protection both inside and outside the United States for disease treatments that prove successful as a matter of public policy regarding worldwide health concerns; and |
| ● | countries other than the United States may have patent laws less favorable to patentees than those upheld by U.S. courts, allowing foreign competitors a better opportunity to create, develop and market competing products. |

​The patent position of biotechnology and pharmaceutical companies generally is highly uncertain, involves complex legal and factual questions and has in recent years been the subject of much litigation. In addition, no consistent policy regarding the breadth of claims allowed in pharmaceutical or biotechnology patents has emerged to date in the U.S. The patent situation outside the U.S. is even more uncertain. The laws of foreign countries may not protect our rights to the same extent as the laws of the U.S., and we may fail to seek or obtain patent protection in all major markets. For example, European patent law restricts the patentability of methods of treatment of the human body more than U.S. law does. Publications of discoveries in the scientific literature often lag behind the actual discoveries, and patent applications in the U.S. and other jurisdictions are typically not published until 18 months after a first filing, or in some cases not at all. Therefore, we cannot know with certainty whether we or our licensors were the first to make the inventions claimed in patents or pending patent applications that we own or licensed, or that we or our licensors were the first to file for patent protection of such inventions. In the event that a third party has also filed a U.S. patent application relating to our product candidates or a similar invention, depending upon the priority dates claimed by the competing parties, we may have to participate in interference proceedings declared by the USPTO to determine priority of invention in the U.S. We might also become involved in derivation proceedings in an event that a third party misappropriates one or more of our inventions and files their own patent application directed to such one or more inventions. The costs of these proceedings could be substantial, and it is possible that our efforts to establish priority of invention (or that a third party derived an invention from us) would be unsuccessful, resulting in a material adverse effect on our U.S. patent position. As a result, the issuance, scope, validity, enforceability and commercial value of our patent rights are highly uncertain. Our pending and future patent applications may not result in patents being issued which protect our technology or products, in whole or in part, or which effectively prevent others from commercializing competitive technologies and products. Changes in either the patent laws or interpretation of the patent laws in the U.S. and other countries may diminish the value of our patents or narrow the scope of our patent protection. For example, the federal courts of the U.S. have taken an increasingly dim view of the patent eligibility of certain subject matter, such as naturally occurring nucleic acid sequences, amino acid sequences and certain methods of utilizing the same, which include their detection in a biological sample and diagnostic conclusions arising from their detection. Such subject matter, which had long been a staple of the biotechnology and biopharmaceutical industry to protect their discoveries, is now considered, with few exceptions, ineligible in the first instance for protection under the patent laws of the U.S. Accordingly, we cannot predict the breadth of claims that may be allowed and remain enforceable in our patents or in those licensed from a third party.​Recent patent reform legislation could increase the uncertainties and costs surrounding the prosecution of our patent applications and the enforcement or defense of our issued patents. On September 16, 2011, the Leahy-Smith America Invents Act, or the Leahy-Smith Act, was signed into law. The Leahy-Smith Act includes a number of significant changes to United States patent law. These include changes to transition from a “first-to-invent” system to a “first inventor-to-file” system and to the way issued patents are challenged. The formation of the Patent Trial and Appeal Board now provides a less burdensome, quicker and less expensive process for challenging issued patents. The USPTO recently developed new regulations and procedures to govern administration of the Leahy-Smith Act, and many of the substantive changes to patent law associated with the Leahy-Smith Act, and in particular, the first inventor-to-file provisions, only became effective on March 16, 2013. Accordingly, it is not clear what, if any, impact the Leahy-Smith Act will have on the operation of our business. However, the Leahy-Smith Act and its implementation could increase the uncertainties and costs surrounding the prosecution of our patent applications and the enforcement or defense of our issued patents, all of which could have a material adverse effect on our business and financial condition.​Even if our patent applications issue as patents, they may not issue in a form that will provide us with any meaningful protection, prevent competitors from competing with us or otherwise provide us with any competitive advantage. Our competitors may be able to circumvent our owned or licensed patents by developing similar or alternative technologies or products in a non-infringing manner.​60
| ● | our licensors might not have been the first to make the inventions covered by each of our pending patent applications and issued patents; |
| ● | our licensors might not have been the first to file patent applications for these inventions; |

| ● | others may independently develop similar or alternative technologies or duplicate our product candidates or any future product candidate technologies; |
| ● | it is possible that none of the pending patent applications licensed to us will result in issued patents; |
| ● | the scope of our issued patents may not extend to competitive products developed or produced by others; |
| ● | the issued patents covering our product candidates or any future product candidate may not provide a basis for market exclusivity for active products, may not provide us with any competitive advantages, or may be challenged by third parties; |
| ● | we may not develop additional proprietary technologies that are patentable; or |
| ● | intellectual property rights of others may have an adverse effect on our business. |

| ● | obtain additional licenses, which may not be available on commercially reasonable terms, if at all; |
| ● | abandon an infringing product candidate or redesign products or processes to avoid infringement, which may demand substantial funds, time and resources and which may result in inferior or less desirable processes and/or products; |
| ● | pay substantial damages, including the possibility of treble damages and attorneys’ fees, if a court decides that the product or proprietary technology at issue infringes on or violates the third party’s rights; |
| ● | pay substantial royalties, fees and/or grant cross-licenses to our product candidates; and/or |
| ● | defend litigation or administrative proceedings which may be costly regardless of outcome, and which could result in a substantial diversion of financial and management resources. |

| ● | the scope of rights granted under such license agreements and other interpretation-related issues; |

| ● | the extent to which our technology and processes infringe on intellectual property of the licensor that is not subject to such license agreements; |
| ● | the scope and interpretation of the representations and warranties made to us by our licensors, including those pertaining to the licensors’ right title and interest in the licensed technology and the licensors’ right to grant the licenses contemplated by such agreements; |
| ● | the sublicensing of patent and other rights under our license agreements and/or collaborative development relationships, and the rights and obligations associated with such sublicensing, including whether or not a given transaction constitutes a sublicense under such license agreement; |
| ● | the diligence and development obligations under license agreements (which may include specific diligence milestones) and what activities or achievements satisfy those diligence obligations; |
| ● | whether or not the milestones associated with certain milestone payment obligations have been achieved or satisfied; |
| ● | the applicability or scope of indemnification claims or obligations under such license agreements; |
| ● | the permissibility and advisability of, and strategy regarding, the pursuit of potential third-party infringers of the intellectual property that is the subject of such license agreements; |
| ● | the calculation of royalty, sublicense revenue and other payment obligations under such license agreements; |
| ● | the extent to which license rights, if any, are retained by licensors under such license agreements; |
| ● | whether or not a material breach has occurred under such license agreements and the extent to which such breach, if deemed to have occurred, is or can be cured within applicable cure periods, if any; |
| ● | disputes regarding patent filing and prosecution decisions, as well as payment obligations regarding past and ongoing patent expenses; |
| ● | intellectual property rights resulting from the joint creation or use of intellectual property (including improvements made to licensed intellectual property) by our and our partners’ licensors and us and our partners; and |
| ● | the priority of invention of patented technology. |

| ● | one or more of our product candidates receive regulatory approval and are approved for commercial sale, due to our need to establish the necessary commercial infrastructure to launch this product candidate without substantial delays, including hiring sales and marketing personnel and contracting with third parties for warehousing, distribution, cash collection and related commercial activities; |
| ● | we are required by the FDA or foreign regulatory authorities to perform studies in addition to those currently expected; |
| ● | there are any delays in completing our clinical trials or the development of any of our product candidates; |
| ● | we execute other collaborative, licensing or similar arrangements that require us to make payments to collaborators or licensors; |
| ● | there are variations in the level of expenses related to our future development programs; |
| ● | there are any product liability or intellectual property infringement lawsuits in which we may become involved; and |
| ● | there are any regulatory developments affecting product candidates of our competitors. |
| ● | obtain regulatory approval for one or more of our product candidates, or any future product candidate that we may license or acquire; |
| ● | manufacture or have manufactured commercial quantities of one or more of our product candidates or any future product candidate, if approved, at acceptable cost levels; and |
| ● | develop a commercial organization and the supporting infrastructure required to successfully market and sell one or more of our product candidates or any future product candidate, if approved. |

Even if we do achieve profitability, we may not be able to sustain or increase profitability on a quarterly or annual basis. Our failure to become and remain profitable would depress the value of our company and could impair our ability to raise capital, expand our business, maintain our research and development efforts, diversify our product offerings or even continue our operations. A decline in the value of our company could also cause you to lose all or part of your investment.​Our short operating history makes it difficult to evaluate our business and prospects.​We have only been conducting operations since our incorporation in March 2015. Our operations to date have been limited to preclinical operations and the in-licensing of our product candidates. We have not yet demonstrated an ability to successfully complete clinical trials, obtain regulatory approvals, manufacture a clinical scale or commercial scale product, or arrange for a third party to do so on our behalf, or conduct sales and marketing activities necessary for successful product commercialization. Consequently, any predictions about our future performance may not be as accurate as they could be if we had a history of successfully developing and commercializing pharmaceutical products.​In addition, as a young business, we may encounter unforeseen expenses, difficulties, complications, delays and other known and unknown factors. We will need to expand our capabilities to support commercial activities. We may not be successful in adding such capabilities.​We expect our financial condition and operating results to continue to fluctuate significantly from quarter to quarter and year to year due to a variety of factors, many of which are beyond our control. Accordingly, you should not rely upon the results of any past quarterly period as an indication of future operating performance.​We do not have any products that are approved for commercial sale and therefore do not expect to generate any revenues from product sales in the foreseeable future, if ever.​We have not generated any product related revenues to date, and do not expect to generate any such revenues for at least the next several years, if at all. To obtain revenues from sales of our product candidates, we must succeed, either alone or with third parties, in developing, obtaining regulatory approval for, manufacturing and marketing products with commercial potential. We may never succeed in these activities, and we may not generate sufficient revenues to continue our business operations or achieve profitability.​We will require substantial additional funding which may not be available to us on acceptable terms, or at all. If we fail to raise the necessary additional capital, we may be unable to complete the development and commercialization of our product candidates, or continue our development programs.​Our operations have consumed substantial amounts of cash since inception. We expect to significantly increase our spending to advance the preclinical and clinical development of our product candidates and launch and commercialize any product candidates for which we may receive regulatory approval, including building our own commercial organizations to address certain markets. We will require additional capital for the further development and, if approved, commercialization of our product candidates, as well as to fund our other operating expenses and capital expenditures. As of September 30, 2020, we had $76.3 million in cash and restricted cash. We cannot provide any assurance that we will be able to raise funds to complete the development of our product candidates. Additionally, we may have to delay or terminate the development of certain product candidates if we are unable to secure additional funding; any such delay or termination, or the announcement of any such delay or termination, may impact our potential growth and have a material adverse effect on the value of our debt and equity securities.​We cannot be certain that additional funding will be available on acceptable terms, or at all. If we are unable to raise additional capital in sufficient amounts or on terms acceptable to us, we may have to significantly delay, scale back or discontinue the development or, if approved, commercialization of one or more of our product candidates. We may also seek collaborators for one or more of our current or future product candidates at an earlier stage than otherwise would be desirable or on terms that are less favorable than might otherwise be available. Any of these events could significantly harm our business, financial condition and prospects.​67
| ● | the timing, design and conduct of, and results from, preclinical studies and clinical trials for our product candidates; |
| ● | the potential for delays in our efforts to seek regulatory approval for our product candidates, and any costs associated with such delays; |
| ● | the costs of establishing a commercial organization to sell, market and distribute our product candidates; |
| ● | the rate of progress and costs of our efforts to prepare for the submission of an NDA or BLA for any product candidates that we may in-license or acquire in the future, and the potential that we may need to conduct additional clinical trials to support applications for regulatory approval; |
| ● | the costs of filing, prosecuting, defending and enforcing any patent claims and other intellectual property rights associated with our product candidates, including any such costs we may be required to expend if our licensors are unwilling or unable to do so; |
| ● | the cost and timing of securing sufficient supplies of our product candidates from our contract manufacturers for clinical trials and in preparation for commercialization; |
| ● | the effect of competing technological and market developments; |
| ● | the terms and timing of any collaborative, licensing, co-promotion or other arrangements that we may establish; |
| ● | if one or more of our product candidates are approved, the potential that we may be required to file a lawsuit to defend our patent rights or regulatory exclusivities from challenges by companies seeking to market generic versions of one or more of our product candidates; and |
| ● | the success of the commercialization of one or more of our product candidates, if approved. |

Raising additional capital may cause dilution to our existing stockholders, restrict our operations or require us to relinquish proprietary rights.​Until such time, if ever, as we can generate substantial product revenue, we expect to finance our cash needs through a combination of equity offerings, debt financings, grants and license and development agreements in connection with any collaborations. To the extent that we raise additional capital through the sale of equity or convertible debt securities, your ownership interest will be diluted, and the terms of these securities may include liquidation or other preferences that adversely affect your rights as a stockholder. Debt financing and preferred equity financing, if available, may involve agreements that include covenants limiting or restricting our ability to take specific actions, such as incurring additional debt, making capital expenditures or declaring dividends.​If we raise additional funds through collaborations, strategic alliances or marketing, distribution or licensing arrangements with third parties, we may have to relinquish valuable rights to our technologies, future revenue streams, research programs or product candidates or grant licenses on terms that may not be favorable to us. If we are unable to raise additional funds through equity or debt financings when needed, we may be required to delay, limit, reduce or terminate our product development or future commercialization efforts or grant rights to develop and market product candidates that we would otherwise prefer to develop and market ourselves.​We will continue to incur significant increased costs as a result of operating as a public company, and our management will be required to devote substantial time to new compliance initiatives.​As a public company, we incur significant legal, accounting and other expenses under the Sarbanes-Oxley Act of 2002, or the Sarbanes-Oxley Act, as well as rules subsequently implemented by the SEC, and the rules of the Nasdaq Stock Exchange. These rules impose various requirements on public companies, including requiring establishment and maintenance of effective disclosure and financial controls and appropriate corporate governance practices. Our management and other personnel have devoted and will continue to devote a substantial amount of time to these compliance initiatives. Moreover, these rules and regulations increase our legal and financial compliance costs and make some activities more time-consuming and costly. For example, these rules and regulations make it more difficult and more expensive for us to obtain director and officer liability insurance, and we may be required to accept reduced policy limits and coverage or incur substantially higher costs to obtain the same or similar coverage. As a result, it may be more difficult for us to attract and retain qualified persons to serve on our board of directors, our board committees or as executive officers.​The Sarbanes-Oxley Act requires, among other things, that we maintain effective internal controls for financial reporting and disclosure controls and procedures. As a result, we are required to periodically perform an evaluation of our internal controls over financial reporting to allow management to report on the effectiveness of those controls, as required by Section 404 of the Sarbanes-Oxley Act. Additionally, our independent auditors are required to perform a similar evaluation and report on the effectiveness of our internal controls over financial reporting. These efforts to comply with Section 404 and related regulations have required, and continue to require, the commitment of significant financial and managerial resources. While we anticipate maintaining the integrity of our internal controls over financial reporting and all other aspects of Section 404, we cannot be certain that a material weakness will not be identified when we test the effectiveness of our control systems in the future. If a material weakness is identified, we could be subject to sanctions or investigations by the SEC or other regulatory authorities, which would require additional financial and management resources, costly litigation or a loss of public confidence in our internal controls, which could have an adverse effect on the market price of our stock.​69
| ● | being permitted to provide only two years of audited financial statements, in addition to any required unaudited interim financial statements, with correspondingly reduced “Management’s Discussion and Analysis of Financial Condition and Results of Operations” disclosure in this Annual Report on Form 10-K; |
| ● | not being required to comply with any requirement that may be adopted by the Public Company Accounting Oversight Board regarding mandatory audit firm rotation or a supplement to the auditor’s report providing additional information about the audit and the financial statements; |
| ● | disclosure obligations regarding executive compensation; and |
| ● | exemptions from the requirements of holding a nonbinding advisory vote on executive compensation and shareholder approval of any golden parachute payments not previously approved. |

| ● | announcements concerning the progress of our efforts to obtain regulatory approval for and commercialize our product candidates or any future product candidate, including any requests we receive from the FDA for additional studies or data that result in delays in obtaining regulatory approval or launching these product candidates, if approved; |
| ● | market conditions in the pharmaceutical and biotechnology sectors or the economy as a whole; |
| ● | price and volume fluctuations in the overall stock market; |
| ● | the failure of one or more of our product candidates or any future product candidate, if approved, to achieve commercial success; |
| ● | announcements of the introduction of new products by us or our competitors; |

| ● | developments concerning product development results or intellectual property rights of others; |
| ● | litigation or public concern about the safety of our potential products; |
| ● | actual fluctuations in our quarterly operating results, and concerns by investors that such fluctuations may occur in the future; |
| ● | deviations in our operating results from the estimates of securities analysts or other analyst comments; |
| ● | additions or departures of key personnel; |
| ● | health care reform legislation, including measures directed at controlling the pricing of pharmaceutical products, and third-party coverage and reimbursement policies; |
| ● | developments concerning current or future strategic collaborations; and |
| ● | discussion of us or our stock price by the financial and scientific press and in online investor communities. |

We might have received better terms from unaffiliated third parties than the terms we receive in our agreements with Fortress.​The agreements we have entered into with Fortress include a Management Services Agreement and the Founders Agreement. While we believe the terms of these agreements are reasonable, they might not reflect terms that would have resulted from arm’s-length negotiations between unaffiliated third parties. The terms of the agreements relate to, among other things, payment of a royalty on product sales and the provision of employment and transition services. We might have received better terms from third parties because, among other things, third parties might have competed with each other to win our business.​The dual roles of our directors who also serve in similar roles with Fortress could create a conflict of interest and will require careful monitoring by our independent directors.​We share some directors with Fortress. This could create conflicts of interest between the two companies in the future. While we believe that the Founders Agreement and the Management Services Agreement were negotiated by independent parties on both sides on arm’s length terms, and the fiduciary duties of both parties were thereby satisfied, in the future situations may arise under the operation of both agreements that may create a conflict of interest. We will have to be diligent to ensure that any such situation is resolved by independent parties. In particular, under the Management Services Agreement, Fortress and its affiliates are free to pursue opportunities which could potentially be of interest to Mustang, and they are not required to notify Mustang prior to pursuing such opportunities. Any such conflict of interest or pursuit by Fortress of a corporate opportunity independent of Mustang could expose us to claims by our investors and creditors and could harm our results of operations.​We may become involved in securities class action litigation that could divert management’s attention and harm our business.​The stock markets have from time to time experienced significant price and volume fluctuations that have affected the market prices for the common stock of biotechnology and pharmaceutical companies. These broad market fluctuations may cause the market price of our stock to decline. In the past, securities class action litigation has often been brought against a company following a decline in the market price of its securities. This risk is especially relevant for us because biotechnology and biopharmaceutical companies have experienced significant stock price volatility in recent years. We may become involved in this type of litigation in the future. Litigation often is expensive and diverts management’s attention and resources, which could adversely affect our business.​
Item 2. Unregistered Sales of Equity Securities and Use of Proceeds
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None.
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Item 3. Defaults Upon Senior Securities
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None.
​
Item 4. Mine Safety Disclosures
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None.
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Item 5. Other Information
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None.
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73
Item 6. Exhibits
​
The exhibits listed on the Exhibit Index are either filed or furnished with this report or incorporated herein by reference.
​
EXHIBIT INDEX
​
| Exhibit No. | Description |
| ​ | ​ | ​ |
| 31.1 | ​ | Certification of President and Chief Executive Officer (Principal Executive Officer), pursuant to Section 302 of the Sarbanes-Oxley Act of 2002 (filed herewith). |
| ​ | ​ | ​ |
| 31.2 | ​ | Certification of Senior Vice President of Finance & Corporate Controller (Principal Financial Officer), pursuant to Section 302 of the Sarbanes-Oxley Act of 2002 (filed herewith). |
| ​ | ​ | ​ |
| 32.1 | ​ | Certification of President and Chief Executive Officer (Principal Executive Officer), pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 (filed herewith). |
| ​ | ​ | ​ |
| 32.2 | ​ | Certification of Senior Vice President of Finance & Corporate Controller (Principal Financial Officer), pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 (filed herewith). |
| ​ | ​ | ​ |
| 101 | ​ | The following financial information from the Company’s Quarterly Report on Form 10-Q for the period ended September 30, 2020, formatted as Inline Extensible Business Reporting Language (iXBRL): (i) the Condensed Balance Sheets, (ii) the Condensed Statements of Operations, (iii) the Condensed Statement of Stockholders’ Equity, (iv) the Condensed Statements of Cash Flows, and (v) Notes to the Condensed Financial Statements (filed herewith). |
| ​ | ​ | ​ |
| 104 | ​ | Cover Page Interactive Data File (formatted as Inline XBRL and contained in exhibit 101) |

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74
| MUSTANG BIO, INC. |
| November 6, 2020 | By: | /s/ Manuel Litchman |
| Manuel Litchman, M.D., President and |
| Chief Executive Officer |
| (Principal Executive Officer) |
| By: | /s/ Brian Achenbach |
| Brian Achenbach |
| Senior Vice President of Finance & Corporate Controller |
| (Principal Financial Officer) |


Question: What is the change in shareholders' equity as a percentage of total assets from December 31, 2019 to September 30, 2020 (in %)?

Solution:
def solution():
     #Define variables name and value

    total_assets_2020 = 86068  # September 30, 2020
    total_assets_2019 = 73445  # December 31, 2019

    shareholders_equity_2020 = 76416  # September 30, 2020
    shareholders_equity_2019 = 51652  # December 31, 2019

    #Do math calculation to get the answer
    Change_2019_2020_equity_pct = ((shareholders_equity_2020 - shareholders_equity_2019) / total_assets_2019) * 100
    return Change_2019_2020_equity_pct


Answer: 33.71774797467493