(1)    Assuming an initial public offering price of $7.00 per share, which is the midpoint of the price range set forth above.

If these existing stockholders were to purchase all of these shares, our executive officers, directors and entities affiliated with our five percent stockholders would beneficially own approximately 62% of our outstanding common stock after this offering.

The calculations of the percentages discussed above and in the table are based on 19,059,288 shares of common stock outstanding after this offering, assuming no exercise of the underwriters’ option to purchase additional shares, and based on shares of common stock deemed outstanding as of August 15, 2013.

However, because indications of interest are not binding agreements or commitments to purchase, the underwriters could determine to sell more, less or no shares to any of these potential investors and any of these potential investors could determine to purchase more, less or no shares in this offering. The underwriting discount for any shares sold to these potential investors in the offering will be the same as the underwriting discount for the shares sold to the public.

We estimate that the net proceeds to us from the sale of 6,666,667 shares of common stock in this offering will be approximately $40.5 million based upon an assumed initial public offering price of $7.00 per share, the midpoint of the price range set forth above, and after deducting estimated underwriting discounts and commissions and estimated offering expenses payable by us. If the underwriters’ option to purchase additional shares in this offering is exercised in full, we estimate that our net proceeds will be approximately $47.0 million, after deducting underwriting discounts and commissions and estimated offering expenses payable by us.

We currently expect to use the net proceeds from this offering as follows:

•     approximately $20.0 million to fund research and development activities to advance our HSC modulation platform and the clinical and preclinical development of its product candidates, including the conduct of our Phase 2 clinical trial of ProHema in patients with orphan hematologic malignancies;

•     approximately $12.0 million to fund research and development activities to advance our SSC modulation platform and the preclinical development of its product candidates, including the conduct of preclinical studies of our Wnt7a analog product candidates; and

•     the remainder for working capital and general corporate purposes, including funding the costs of operating as a public company.

The expected use of net proceeds from this offering represents our intentions based upon our current plans and business conditions, which could change in the future as our plans and business conditions evolve. The amounts and timing of our actual expenditures may vary significantly depending on numerous factors, including the progress of our development, the status of and results from clinical trials and preclinical studies, as well as any collaborations that we may enter into with third parties for our product candidates, the amount of cash available from other sources and any unforeseen cash needs. As a result, our management will retain broad discretion over the allocation of the net proceeds from this offering.

Assuming an initial public offering price of $7.00 per share, which is the midpoint of the price range set forth above, as of June 30, 2013, on a pro forma as adjusted basis, cash and cash equivalents would have been approximately $64.9 million, additional paid-in capital would have been approximately $136.0 million, total stockholders’ equity (deficit) would have been approximately $61.0 million, and total capitalization would have been approximately $63.7 million.

The pro forma as adjusted capitalization information above assumes (i) the issuance of 3,394,138 shares of common stock upon the conversion of an aggregate of $23.7 million in principal and accrued interest on our 2013 Notes upon the completion of

this offering at the assumed initial public offering price of $7.00 per share, (ii) that the offering is completed on October 4, 2013 and (iii) our repayment in cash of approximately $0.1 million in principal and accrued interest under our 2013 Notes issued in August 2013 in lieu of the issuance of 8,351 shares of common stock upon the conversion of such notes which, if issued, would cause the holders of such notes, together with their affiliates and related parties, to beneficially own 15% or more of our outstanding common stock following the completion of this offering.

The number of shares to be issued upon the automatic conversion of our 2013 Notes upon the completion of this offering depends in part on the initial public offering price of our common stock and the date on which this offering is completed. In addition, the number of shares of common stock to be issued upon the conversion of our convertible promissory notes issued in August 2013 immediately following the completion of this offering cannot cause the holders of these notes to beneficially own 15% or more of our outstanding common stock. As a result, the actual number of shares of common stock issued upon such conversion may differ from the number of shares set forth above. A $1.00 increase in the assumed initial public offering price of $7.00 per share would decrease by 416,965 shares the aggregate number of shares of our common stock issuable upon the automatic conversion of the outstanding principal and accrued interest on our 2013 Notes and decrease by approximately $0.1 million the principal and accrued interest under such notes that we would be required to repay on or before the date 30 days after the completion of this offering. A $1.00 decrease in the assumed initial public offering price of $7.00 per share would increase by 105,182 shares the aggregate number of shares of our common stock issuable upon the automatic conversion of the outstanding principal and accrued interest on our 2013 Notes and increase by approximately $2.7 million the principal and accrued interest under such notes that we would be required to repay in lieu of the issuance of 470,251 shares of common stock, which, if issued, would cause the holders of such notes and their affiliates and related parties to beneficially own 15% or more of our outstanding common stock, on or before the date 30 days after the completion of this offering.