Company: SION
Filing Date: 2025-01-17
Form Type: S-1
Source: 0001193125-25-008474
Chunk: 141

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-01-17
Form: S-1
Chunk 141
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 ) |     | $      | (7,023 | ) |

101

Research and Development Expenses The following table summarizes our research and development expenses (in thousands):

|                                                        |     | Year Ended December 31, |   2023 |     |   |   2022 |     |   | Change |   |
|:-------------------------------------------------------|:----|:------------------------|-------:|:----|:--|-------:|:----|:--|-------:|:--|
| Direct research and development expenses by program:   |     |                         |        |     |   |        |     |   |        |   |
| NBD1 programs                                          |     | $                       | 26,357 |     | $ | 19,794 |     | $ |  6,563 |   |
| Complementary modulator programs                       |     |                         |  2,056 |     |   |  5,541 |     |   | (3,485 | ) |
| Unallocated research and development expenses:         |     |                         |        |     |   |        |     |   |        |   |
| Personnel-related (including stock-based compensation) |     |                         |  8,681 |     |   |  7,068 |     |   |  1,613 |   |
| Facility, lab and depreciation                         |     |                         |  2,004 |     |   |    777 |     |   |  1,227 |   |
| Other R&D related costs                                |     |                         |  1,528 |     |   |  1,425 |     |   |    103 |   |
| Total research and development expenses                |     | $                       | 40,626 |     | $ | 34,605 |     | $ |  6,021 |   |

Research and development expenses increased by $6.0 million to $40.6 million for the year ended December 31, 2023 from $34.6 million for the year ended December 31, 2022. The increase in research and development expenses was primarily due to direct research and development expenses of:

| • |     | $6.6 million increase in NBD1 program costs due to initiation of the Phase 1 clinicial trial of our first-generation 
 NBD1 stabilizer and ongoing IND-enabling activities for SION-719 and