Boundless Bio (BOLD) SEC Filings

Boundless Bio, Inc. (BOLD) has proposed a merger with Serapha Bio, Inc. Under the agreement, Boundless Bio’s wholly owned Merger Sub would merge into Serapha, with Serapha surviving as Boundless Bio’s wholly owned subsidiary, subject to satisfaction or waiver of the agreement’s conditions.

Boundless Bio has filed an S-4 registration statement containing a proxy statement/prospectus, but the SEC has not declared it effective and its contents may change. Closing also depends on stockholder approvals and other conditions, including approval of the Nasdaq listing application. Serapha’s communication describes the ongoing SERP-01 investigator-initiated trial as early-stage, limited in patient number, conducted by third parties, and not designed to support regulatory approval or predict results of planned trials.

Boundless Bio, Inc. (BOLD) reported indirect purchases totaling 21,640 common shares by Kevin Tang and Tang Capital Management LLC, each identified as a 10% owner: 5,800 shares on October 22, 6,234 on October 23, and 9,606 on October 26, 2026. The reported per-share prices were $2.40, $2.38, and $2.38, respectively. Footnotes give purchase-price ranges of $2.39 to $2.40, $2.36 to $2.40, and $2.37 to $2.40 for those dates, respectively; the October 22 price is described as a weighted-average price. No Rule 10b5-1 plan is reported.

Boundless Bio, Inc. furnished Serapha Bio’s interim clinical update on SERP-01 in connection with their proposed merger. The update reports data from an ongoing investigator-initiated trial of four PiZZ participants receiving one dose of the investigational base-editing therapy.

As of October 15, 2026, total serum AAT exceeded the 11 µM protective threshold in all four participants. By week 3, M-AAT was 98.7% at 35 mg and 93.4% at 45 mg; in the 45 mg cohort, total AAT was at or near the 20 µM lower limit of normal through up to 10 months of follow-up. A biopsy at 10 weeks from the 35 mg participant showed 54% target-site correction, with no bystander editing detected at neighboring bases. No serious adverse events or treatment-related adverse events of grade 3 or higher were observed as of October 15, 2026. Serapha intends to initiate a U.S. Phase 2/3 trial in late 2026 or early 2027. The proposed merger remains subject to satisfaction or waiver of Merger Agreement conditions, and the related S-4 has not yet been declared effective.

Boundless Bio, Inc. ten-percent owners Kevin Tang and Tang Capital Management LLC reported four indirect purchases totaling 149,474 common shares from October 16 through October 20, 2026. The entries were 118,185 shares on October 16 at a weighted-average $2.34 per share; 12,790 shares on October 19 at $2.34; 18,279 shares that day at $2.33; and 220 shares on October 20 at $2.37. Footnotes give the respective transaction price ranges as $2.31–$2.35, $2.31–$2.35, $2.32–$2.35, and $2.33–$2.40. A footnote identifies Kevin Tang’s pecuniary interest in shares beneficially held by Tang Capital Partners, LP; Tang Capital Partners International, LP; Tang Capital Partners III, Inc.; and Tang Capital Partners IV, Inc. The reporting persons stated they delivered $1,723.10 to Boundless Bio. No Rule 10b5-1 plan is reported.

Boundless Bio, Inc. (BOLD) has proposed a merger with Serapha Bio, Inc., subject to stockholder approval and other closing conditions. At closing, Boulder Merger Sub will merge into Serapha, which will survive as Boundless Bio’s wholly owned subsidiary. Boundless Bio is expected to be renamed Serapha Bio and trade as AATD on Nasdaq if listing is approved. The estimated exchange ratio is approximately 8.6737 Boundless Bio shares per Serapha share, based on capitalization as of October 1, 2026; it excludes the proposed reverse split and may adjust based on Boundless Bio Net Cash at closing.

Serapha investors invested approximately $138 million in a Series A financing and agreed to buy approximately $92 million of pre-closing securities, subject to closing conditions. Fully diluted ownership is expected to be 3.8% for pre-merger Boundless Bio holders, 29.3% for former Serapha holders excluding the financing, and 66.9% for financing securities. Boundless Bio expects a pre-closing dividend of approximately $44 million to $48 million if Proposals 1, 2 and 3 are approved. The combined company plans to focus on Serapha’s SERP-01 AATD program and does not intend to continue Boundless Bio’s legacy ecDTx development. As of August 6, 2026, SERP-01 had preliminary evidence of near-normal serum AAT levels among four treated patients, with no serious adverse events reported; Serapha cautioned that results may not be replicated in larger trials.

Boundless Bio, Inc. (BOLD) amended its Merger Agreement with Serapha Bio, Inc. and Boulder Merger Sub Corp. on August 28, 2026. The amendment clarifies definitions around the Company Pre-Closing Financing and confirms that required minimum aggregate cash proceeds must be received at or around closing.

The amendment specifies that all outstanding Serapha restricted stock units will convert at closing into Boundless Bio restricted stock units, with share counts adjusted by the Exchange Ratio while preserving vesting and acceleration terms. It also introduces mechanics to deliver a portion of the Merger Consideration as pre-funded warrants with a de minimis exercise price instead of common stock when needed to keep each holder below its elected Beneficial Ownership Limitation.

In addition, the voting standard to increase Boundless Bio’s authorized common shares is changed to a majority of shares properly cast, rather than a majority of all shares outstanding. The filing includes a detailed form of pre-funded warrant that is subject to ownership caps, anti-dilution adjustments and allows cashless exercise.

Boundless Bio, Inc. (BOLD) reports that on August 28, 2026 it entered into Amendment No. 1 to its Agreement and Plan of Merger and Reorganization with Boulder Merger Sub Corp. and Serapha Bio, Inc. The amendment refines mechanics around the planned merger under which Serapha will become a wholly owned subsidiary of Boundless Bio.

The amendment clarifies definitions and provisions related to the planned Company Pre-Closing Financing, specifies that all outstanding Serapha restricted stock units will convert into Boundless Bio restricted stock units adjusted by the Exchange Ratio, and introduces pre-funded warrants with a $0.00001 per-share exercise price as merger consideration when issuing common stock would breach a holder’s Beneficial Ownership Limitation. It also lowers the voting standard for increasing authorized Boundless Bio common shares to a majority of shares properly cast, rather than a majority of shares outstanding and entitled to vote. All other merger terms remain as previously disclosed. The company highlights multiple risks that could affect completion and outcomes of the merger and related financing, including regulatory approvals, satisfaction of closing conditions, exchange ratio adjustments, market price movements, and potential non-consummation of the pre-closing financing.

Boundless Bio, Inc. (BOLD) had a significant shareholder group associated with Kevin Tang report the sale of 18,300 shares of Common Stock on 2026-08-26 at a weighted-average price of $2.97 per share, in transactions ranging from $2.90 to $3.03. Following this sale, entities affiliated with Tang Capital Partners beneficially hold 2,840,635 shares of Boundless Bio indirectly through several Tang Capital entities. The reporting persons stated they delivered to Boundless Bio the full disgorgeable profit of $10,046.70 arising from this sale and indicated that the transactions were not effected under a Rule 10b5-1 trading plan.

Boundless Bio, Inc. (BOLD) discloses that Zachary Hornby has filed a Schedule 13G reporting beneficial ownership of its common stock. As of August 17, 2026, he beneficially owns 2,426,857 shares of common stock, including stock options exercisable within 60 days, representing 9.8% of the outstanding class based on 22,747,985 shares outstanding as of August 5, 2026. He reports sole voting and dispositive power over all of these shares and no shared voting or dispositive power.