Bambusa Therapeutics, Inc.

The following table summarizes our cash and cash equivalents and marketable securities and capitalization as of June 30, 2026:

•on an actual basis;

•on a pro forma basis to give effect to (1) the Preferred Stock Conversion and (2) the filing and effectiveness of our amended and restated certificate of incorporation, each of which will occur immediately prior to the completion of this offering; and

•on a pro forma as adjusted basis to reflect (1) the pro forma adjustments set forth above and (2) the issuance and sale by us of shares of common stock in this offering at the assumed initial public offering price of $ per share, which is the midpoint of the price range set forth on the cover page of this prospectus, and after deducting estimated underwriting discounts and commissions and estimated offering expenses payable by us.

You should read this table together with our consolidated financial statements and the related notes included elsewhere in this prospectus and the section titled “Management’s Discussion and Analysis of Financial Condition and Results of Operations.”

(1)Each $1.00 increase or decrease in the assumed initial public offering price of $ per share, which is the midpoint of the price range set forth on the cover page of this prospectus, would increase or decrease, as applicable, each of our cash and cash equivalents and marketable securities, additional paid-in capital, total stockholders’ (deficit) equity, and total capitalization by $ million, assuming that the number of shares offered by us, as set forth on the cover page of this prospectus, remains the same, and after deducting estimated underwriting discounts and commissions and estimated offering expenses payable by us. Similarly, each increase or decrease of 1.0 million in the number of shares offered by us would increase or decrease, as applicable, each of our cash and cash equivalents and marketable securities, additional paid-in capital, total stockholders’ (deficit) equity, and total capitalization by $ million, assuming that the assumed initial public offering price remains the same, and after deducting the estimated underwriting discounts and commissions and estimated offering expenses payable by us. The pro forma as adjusted information discussed above is illustrative only and will adjust based on the actual initial public offering price and other terms of this offering determined at pricing.

The foregoing tables and calculations are based on 25,740,828 shares of our common stock outstanding as of June 30, 2026 (which includes 1,855,651 shares of unvested restricted common stock), after giving effect to the Preferred Stock Conversion, and excludes:

• shares of common stock issuable upon the exercise of options approved subsequent to June 30, 2026, which were granted contingent and effective upon the pricing of this offering with a price per share equal to the initial public offering price (the “IPO Options”);

• shares of common stock issuable upon the vesting and settlement of performance-based restricted stock units (“RSUs”) approved subsequent to June 30, 2026, which were granted in connection with the pricing of this offering (the “IPO PSUs”);

• shares of common stock reserved for future issuance under the 2026 Plan (which include the shares issuable under the IPO Options and the IPO PSUs), which will become effective on the business day immediately prior to the date of effectiveness of the registration statement of which this prospectus forms a part;

• shares of common stock reserved for future issuance under the 2024 Plan, as of , 2026, which, to the extent such shares remain available under the 2024 Plan as the effectiveness of the 2026 Plan, will be added to the shares of our common stock to be reserved under the 2026 Plan, upon its effectiveness, at which time we will cease granting awards under our 2024 Plan;

• shares of common stock reserved for future issuance under the ESPP, which will become effective on the business day immediately prior to the date of effectiveness of the registration statement of which this prospectus forms a part; and

•securities or other consideration which may be issuable upon the settlement of outstanding VARs as of June 30, 2026.

The 2026 Plan and the ESPP each provide for annual automatic increases in the number of shares of our common stock reserved thereunder, and the 2026 Plan also provides for increases to the number of shares of our common stock that may be granted thereunder based on shares underlying the awards granted under the 2024 Plan that expire, are forfeited, or are repurchased by us, as more fully described in the section titled “Executive Compensation—Employee Benefit and Stock Plans.”