Amendment 1 (this Amendment) to the Development and Clinical Supply Agreement with the Contract Number: E86A1D4C-B3F9 Between Ultragenyx Pharmaceutical Inc. 60 Leveroni Court, Novato, CA 94949, USA (Ultragenyx) and Rentschler Biotechnologie GmbH, Erwin-Rentschler-Str. 21, 88471 Laupheim, Germany (Rentschler)

Exhibit 10.34

Amendment 1 (“this Amendment”)
to the Development and Clinical Supply Agreement
with the Contract Number: E86A1D4C-B3F9

Between

Ultragenyx Pharmaceutical Inc.
60 Leveroni Court, Novato, CA 94949, USA
(“Ultragenyx’’)

and

Rentschler Biotechnologie GmbH,
Erwin-Rentschler-Str. 21, 88471 Laupheim, Germany
(“Rentschler’’)

Rentschler and/or Ultragenyx are hereinafter referred to as “Party” or “Parties”.

The Parties amend their Development and Clinical Supply Agreement with the Contract Number: E86A1D4C-B3F9, effective as of 31 August 2012, (“the Agreement”) as follows:

If (1) Ultragenyx cancels or postpones the Services concerning Drug Product for a rea­ son within Ultragenyx’s control and not the result of Rentschler’s policies, or (2) other deviations to the respective timelines stated in Schedule Two are caused by reasons within Ultragenyx’s control and not the result of Rentschler’s policies, then in either case, Rentschler is entitled to require that Ultragenyx pay the following reimbursement for the unused production facilities:

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Rentschler shall use commercially reasonable efforts to mitigate any losses or damages it may incur due to Ultragenyx’s cancellation or postponement regarding the Drug Product. If Rentschler mitigates such losses or damages so that it incurs no damage or significantly less damage as a result of the cancellation or postponement in the provision of materials or information, Ultragenyx must only reimburse Rentschler for the unmitigated costs of the cancellation or postponement. This in particular applies if Rentschler can use the production time for another order.

For clarity, if Ultragenyx notifies Rentschler of a cancellation or postponement prior to the thirteenth week before the production time, then the foregoing reimbursement shall not be owed to Rentschler; provided, however, that any actual expenses for activities performed by Rentschler with regard to the cancelled or postponed batch (e.g. preparation of manufacturing documentation) shall be borne by Ultragenyx and may be invoiced by Rentschler to Ultragenyx.

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