EXHIBIT 10.1

HOBBS BROOK OFFICE PARK
333 Wyman Street, Waltham, Massachusetts

FIRST AMENDMENT TO LEASE
Altus Pharmaceuticals, Inc.

This First Amendment to Lease (the “Amendment”) is made as of the 30th day of
June, 2009 (the “Execution Date”), by and between 275 Wyman LLC, a Delaware
limited liability company (“Landlord”) and Altus Pharmaceuticals Inc., a
Delaware corporation (“Tenant”).

Background

Reference is made to a lease dated October 29, 2007 (the “Lease”) between
Landlord and Tenant for certain premises containing 83,405 square feet of
Rentable Floor Area (the “Premises”) in the building known as 333 Wyman Street,
Waltham, Massachusetts (the “Building”). Capitalized terms used and not
otherwise defined in this Amendment shall have the meanings ascribed to them in
the Lease.

Landlord and Tenant desire to enter into this Amendment to amend the terms and
provisions of the Lease as more particularly set forth in this Amendment.

Agreement

FOR VALUE RECEIVED, Landlord and Tenant agree as follows:

1. Additional Payment. On the Execution Date, Tenant has paid to Landlord the
sum of One Million Twenty-Five Thousand and No/100 Dollars ($1,025,000.00) (the
“Additional Payment”). Provided that Tenant is not in default under the Lease
and no Insolvency Event (defined below) has occurred, Tenant shall not be
obligated to make additional payments of monthly installments of Annual Fixed
Rent during the months of June, July, August, September and October of 2009.
Provided that Tenant is not in default under the Lease and no Insolvency Event
has occurred, Landlord will apply the Additional Payment to the payment of
Annual Fixed Rent when due under the Lease. Tenant shall resume monthly payments
of Annual Fixed Rent on November 2, 2009 if this Lease has not terminated under
the provisions of Paragraph 2 of this Amendment. Without limiting any provisions
of the Lease concerning default, from and after the occurrence of a default
under the Lease, Tenant shall commence payments of Annual Fixed Rent. Portions
of the Additional Payment not previously applied by Landlord against the payment
of Annual Fixed Rent shall constitute additional Security Deposit under the
Lease, including, without limitation, Section 8.18 of the Lease and Paragraph 4
of this Amendment. Without limiting the generality of the foregoing, after a
default by Tenant under the Lease or if an Insolvency Event or Disgorgement
Demand occurs, Landlord may, but shall not be obligated to, apply all or any
portion of the Additional Payment to pay any amount due Landlord under the
Lease, including, without limitation, Agreed Termination Damages and amounts
subject to Disgorgement Demand (defined below).

2. Agreed Termination Damages. Landlord and Tenant stipulate and agree that
Landlord’s damages for early termination of the Lease are Three Million Six
Hundred Thirty-Two Thousand Eight Hundred Nine and 02/100 Dollars
($3,632,809.02) (the “Agreed Termination Damages”), which is calculated using
the methodology under Section 365 of the United States Bankruptcy Code as if the
Lease were rejected in a Tenant’s bankruptcy proceeding. The Agreed Termination
Damages do not include damages for leasing commissions, damage to the Premises,
personal property removal and disposition costs, and other amounts not included
within the cap for lease rejection damages under Section 502(b)(6) of the
Bankruptcy Code and nothing herein shall be deemed a waiver of Landlord’s rights
to recover such amounts from Tenant. Landlord and Tenant agree that Agreed
Termination Damages are a reasonable estimate of the damages to be suffered by
Landlord for loss of rent due to the premature termination of the Lease, and
that the Agreed Termination Damages do not constitute a penalty. (The Agreed
Termination Damages do not apply in the case of any right under the Lease of
Tenant to terminate in the event of a casualty.) Notwithstanding the foregoing,
Landlord agrees to accept the amount of Four Hundred and Seventy-Five Thousand
Dollars and 00/100 Dollars ($475,000.00) (the “Reduced Damages Amount”) only if
all of the following conditions are met on or before the Outside Date (defined
below): (a) Tenant has not been in default under the Lease on or after the
Execution Date (provided that Tenant shall have the right to cure a default
within two (2) business days of such default if such default is curable by the
payment of money) and no event has occurred that, with the passage of time, the
giving of notice, or both, could become a default under the Lease, (b) no
Insolvency Event has occurred, (c) no notice has been given or claim made
asserting that any payment or property received by Landlord under the Lease is
fraudulent, preferential or should be paid, remitted, returned or disgorged
under the Bankruptcy Code or other applicable law (a “Disgorgement Demand”),
whether before the Early Termination Date or during the Security Deposit
Retention Period (defined below), (d) Tenant shall have delivered two (2) copies
of the Termination Agreement and the Termination of Notice of Lease in the forms
attached as Exhibit 1 hereto, each bearing original signatures of Tenant,
(e) Tenant shall have paid to Landlord the sum of $475,000 in immediate,
same-day United States funds wired for credit into Landlord’s bank account in
accordance with wire instructions attached hereto as Exhibit 2, or according to
such other instructions as Landlord may give by written notice to Tenant, and
(f) Tenant shall have returned the Premises to Landlord in accordance with the
terms of the Lease, including, but not limited to, Section 5.10 and Paragraph 3
below. As used herein, “Insolvency Event” means Tenant becomes a party to any
action or proceeding under the bankruptcy, insolvency or reorganization laws of
the United States or any state thereof. For the purposes of this Paragraph 2,
“Outside Date” means the earliest of (x) the date that Tenant shall close one or
more capital raising transactions that result in gross proceeds of at least
Twenty Five Million and No/100 Dollars ($25,000,000.00) or engage in a merger,
sale or similar transaction (collectively, a “Financing”) and (y) 3:00 P.M.
Waltham, Massachusetts time on November 2, 2009, time being of the essence. If
all of the foregoing conditions are satisfied on or before the Outside Date,
then the Lease shall terminate, subject to the terms and provisions hereof,
including, without limitation, Paragraph 8, at 11:59 p.m. on the date all such
conditions were satisfied, as evidenced by the date written by Landlord as the
“Effective Date” set forth in the Termination Agreement countersigned by
Landlord and returned to Tenant (the “Early Termination Date. If Landlord
receives notice at least five (5) Business Days in advance of Tenant’s intention
to satisfy all of the foregoing conditions on a specified business day on or
before the Outside Date, Landlord agrees to submit a countersigned original of
the Termination Agreement to the Boston office of Stewart Title Guaranty Company
as escrow agent, to be delivered by Escrow Agent to Tenant upon direction from
Landlord that all of the foregoing conditions have been satisfied, provided that
Tenant shall pay the costs of the Escrow Agent and that Landlord, Tenant and
Escrow Agent shall have entered into an escrow agreement substantially in the
form attached hereto as Exhibit 3. With respect to the period following the
Early Termination Date, all rights and obligations of Landlord and Tenant shall
terminate as though such date were the Term Expiration Date (as defined in the
Lease), except (i) as set forth in this Amendment, (ii) the obligations under
the Lease that arise during or are otherwise attributable to the period ending
on such Early Termination Date, and (iii) the obligations that are specified in
the Lease to survive the termination or expiration of the Lease. Failure to
satisfy all of the conditions set forth in this Paragraph 2 and pay the Reduced
Damages Amount upon the occurrence of a Financing shall constitute an immediate
default under the Lease, without notice or cure period. If Tenant fails to
satisfy all of the conditions set forth in this Paragraph 2 on or before the
Outside Date, then Landlord’s agreement to accept the Reduced Damages Amount and
execute and deliver the Termination Agreement shall, at Landlord’s option, be
void and Landlord shall be entitled at its sole discretion to exercise all or
any of its rights and remedies under the Lease including without limitation to
receive from Tenant the Agreed Termination Damages. Tenant shall execute and
deliver such additional documentation as Landlord reasonably requires to
evidence the termination of the Lease and terminate any Notice of Lease of
record. Upon Tenant’s delivering the Termination Agreement, any and all rights
of Tenant to extend the Lease Term shall immediately be void and of no further
force or effect. Tenant hereby acknowledges and agrees that Tenant shall not be
entitled to any rebate or return of any portion of the Agreed Termination
Damages for any reason.

3. Surrender of Property. Tenant shall leave the fixtures, furnishings and
equipment (“F,F&E”) that is in the Premises on the Execution Date, and any F,F&E
that Tenant adds to the Premises after the Execution Date, in place in the
Premises on the Early Termination Date. If Landlord shall notify Tenant in
writing on or before the ninetieth (90th) day after the Early Termination Date
that Tenant shall remove F,F&E, or any other Tenant alterations and additions
that pursuant to the terms of the Lease are to be removed by Tenant upon
surrender of the Premises, then Tenant shall properly remove the F,F&E and other
alterations and additions specified by Landlord at Tenant’s sole cost and
expense within a reasonable time after Landlord’s notice, not to exceed thirty
(30) days. Landlord agrees that if Landlord requires Tenant to remove cabling in
the Premises, Tenant shall properly remove the cabling running from the
telephone/data closets in the Building to the termination points of the cabling
at the workstations within the Premises. Tenant shall remove such F,F&E and
alterations and additions and restore the Premises in compliance with the terms
and provisions of the Lease, including, without limitation, Section 5.10. Such
property left in the Premises shall become the property of Landlord. Tenant
shall promptly execute and deliver to Landlord such documentation as Landlord
reasonably requests in connection with the transfer of F,F&E and other property
to Landlord. The provisions of this Paragraph 3 shall survive the expiration or
early termination of the Lease.

4. Security Deposit. The Security Deposit, including, without limitation, the
Letter of Credit Security Deposit, secures the performance of all of the
obligations of Tenant under the Lease, including, without limitation, the
Additional Payment, the Agreed Termination Damages, the Reduced Damages Amount
(as defined above), costs incurred in connection with Tenant’s failure to comply
with Paragraph 3 above, and any amounts or property transfers that are the
subject of a Disgorgement Demand. In no event shall the Security Deposit
required under the Lease be reduced by or for Tenant and the last paragraph of
Section 8.18 of the Lease is hereby deleted. If this Lease terminates on the
Early Termination Date pursuant to the provisions of Paragraph 2 of this
Amendment, and if the Early Termination Date occurs on or before November 2,
2009, then, provided that Tenant has timely vacated and surrendered the
Premises, has complied with its obligations under the Lease and provided further
that as of March 31, 2010 (the “Security Deposit Retention Period”) there has
not occurred an Insolvency Event or Disgorgement Demand, and Tenant so certifies
to Landlord, then Landlord shall deliver the Letter of Credit Security Deposit
to Tenant (net of amounts Landlord is entitled to deduct therefrom, if any).
Without limiting the generality of any provision of the Lease, including without
limitation Section 8.18, if an Insolvency Event or Disgorgement Demand shall
occur, then Landlord may, but shall not be obligated to, draw on the Letter of
Credit Security Deposit and hold the proceeds as commingled cash Security
Deposit under Section 8.18 of the Lease for the performance by Tenant of its
obligations under the Lease, including, without limitation for the payment of
any amounts subject to a Disgorgement Demand, or apply the amount so drawn to
pay any amounts due Landlord under the Lease. In no event shall Landlord be
obligated to return to Tenant all or any portion of any Security Deposit if an
Insolvency Event should be pending or if a final non-appealable court order has
not been entered which holds that Landlord has no obligation to return any funds
or property that are the subject of a Disgorgement Demand. Tenant agrees that
the security deposit (the “610 Security Deposit”) under that certain lease dated
as of October 29, 2007, as amended, between 610 Lincoln LLC and Tenant for
premises within the building known as 610 Lincoln Street North, Waltham,
Massachusetts (the “610 Lease”) shall also serve to secure all of the
obligations of Tenant under this Lease with respect to all amounts and property
that become the subject of a Disgorgement Demand and that, if a Disgorgement
Demand is made, Landlord shall have the same rights with respect to the 610
Security Deposit as Landlord has with respect to the Security Deposit under this
Lease. After a final non-appealable court order has been entered which holds
that Landlord has no obligation to return funds or property that were the
subject of a Disgorgement Demand, Landlord shall return the 610 Security Deposit
(or portion thereof) received by Landlord under the preceding sentence, net of
Landlord’s costs incurred in connection with such Disgorgement Demand, to the
party entitled to the 610 Security Deposit under the 610 Lease. Tenant has
agreed with 610 Lincoln LLC in the 610 Lease that the Security Deposit hereunder
shall also secure all of the obligations of Tenant with respect to all amounts
and property that become the subject of a “Disgorgement Demand” as defined under
the 610 Lease. In furtherance of foregoing, Tenant agrees that Landlord shall be
entitled to draw upon the Letter of Credit Security Deposit and to turn over the
proceeds and all or any other portion of the Security Deposit to 610 Lincoln
LLC, when directed by 610 Lincoln LLC pursuant to its rights with respect to the
Security Deposit under the 610 Lease.

5. Amended Provisions. The following provisions of the Lease are hereby amended
as follows:

(a) Section 2.1.1 is hereby deleted in its entirety.

(b) Section 7.1 is hereby amended by deleting paragraph (a) of Section 7.1 and
replacing it with the following:

“7.1(a) if Tenant shall fail to perform or observe any of Tenant’s covenants,
and if such failure shall continue, (a) in the case of installments of Annual
Fixed Rent, for more than five (5) days after the date due to be paid under the
Lease (without the right of Tenant to receive notice therefor), (b) in the case
of all other Rent or any other sum due Landlord under the Lease, for more than
five (5) Business Days after Landlord’s notice is given, or (c) in any other
case, after notice, for more than thirty (30) days (provided that if correction
of any such matter reasonably requires longer than thirty (30) days and Tenant
so notifies Landlord within twenty (20) days after Landlord’s notice is given
together with an estimate of time required for such cure, Tenant shall be
allowed such longer period, but only if cure is begun and diligently pursued
within such thirty (30) day period and such delay does not cause increased risk
of damage to person or property), or”

6. Brokerage. Landlord and Tenant each represent and warrant that it has had no
dealings with any broker or agent in connection with this Amendment, except
Wyman Street Advisors (the “Broker”). Tenant and Landlord each covenants to the
other to defend (by counsel reasonably approved by the indemnitee), pay, hold
harmless and indemnify the other from and against any and all costs, expense or
liability for any compensation, commissions, and charges claimed by any broker
or agent, with respect to this Amendment or the negotiation thereof arising from
a breach of the foregoing warranty. Landlord shall pay all commissions due to
the Broker in connection with this Amendment.

7. Representations and Warranties. Tenant represents and warrants to Landlord
that (i) the person executing this Amendment on behalf of Tenant is duly
authorized and has full power to execute and deliver this Amendment, and (ii) as
of the Execution Date, Landlord is not in default of its obligations under the
Lease and no event or condition exists which with notice and the passage of time
would constitute such a default by Landlord and Tenant has no claim, offset, or
defense against the enforcement of the Lease in accordance with its terms.
Tenant further hereby confirms and agrees that there are no liabilities,
amounts, or payments of any kind that are due and owing from Landlord to Tenant
on account of any conditions, events, or course of conduct with respect to the
Premises (or any portion thereof) or the Lease with respect to the period ending
on the Execution Date, including, without limitation, for any amounts on account
of tenant improvements, operating expenses or taxes, or prior efforts by Tenant
to sublease all or part of the Premises, and Tenant hereby waives any claims
that Tenant may have with respect to any and all such matters. Landlord
represents and warrants to Tenant (a) that the person executing this Amendment
on behalf of Landlord is duly authorized and has full power to execute and
deliver this Amendment and (b) as of the Execution Date, there is no mortgage
encumbering the Building or the Land.

8. Disgorgement. If a Disgorgement Demand is made, or if Landlord is otherwise
for any reason forced to disgorge any portion of any payment provided for under
this Amendment, and if Landlord has returned the Security Deposit after
expiration of the Security Deposit Retention Period or the Letter of Credit
Security Deposit has expired, then at Landlord’s election Landlord shall be
entitled to exercise all or any of its rights and remedies under the Lease
including without limitation immediately to receive from Tenant the full Agreed
Termination Damages and all other damages to Landlord that are not included in
the capped lease rejection damages under Section 502(b)(6) of the United States
Bankruptcy Code. The provisions of this Paragraph 8 shall survive the expiration
or early termination of the Lease.

9. Landlord’s Costs and Expenses. Without limiting the generality of any
provision of the Lease, Tenant shall promptly pay all costs and expenses
(including, without limitation, attorneys fees) incurred by or for Landlord in
connection with any Disgorgement Demand, Insolvency Event or any enforcement of
Landlord’s rights under the Lease and no provision of this Amendment shall be
construed in any way that limits Landlord’s recovery for such amounts or that
reduces by such amounts any other payments to which Landlord is entitled
hereunder. The provisions of this Paragraph 9 shall survive the expiration or
early termination of the Lease.

10. Letter of Credit. Tenant covenants and agrees that Tenant shall use
commercially reasonable efforts to obtain a replacement Letter of Credit from
Bank of America with the changes required by Landlord, and attached to this
Amendment as Exhibit 4 by July 14, 2009. In addition to the foregoing, Tenant
acknowledges that the Letter of Credit provided to Landlord under the Lease in
2007 contains a typographical error: the existing Letter of Credit refers to
“610 Lincoln LLC” and the parties intended it to refer to “275 Wyman LLC”.
Tenant agrees that Landlord may draw upon such Letter of Credit when Landlord is
entitled to make a draw under this Lease by presenting a statement that includes
the text specified in the Letter of credit, including the erroneous reference to
“610 Lincoln LLC”. In addition, Tenant agrees that in each instance in which
Landlord is entitled to draw upon the Letter of Credit Security Deposit under
the Lease, Landlord shall be entitled to use the text required under the Letter
of Credit Security Deposit in Landlord’s statement to be presented in connection
with a draw upon the Letter of Credit Security Deposit whether or not such text
describes the circumstances of such draw. As between Landlord and Tenant, the
terms and provisions of the Lease govern the rights of Landlord to draw upon the
Letter of Credit Security Deposit.

11. Ratification. Except as expressly set forth herein, the Lease as originally
executed and previously amended is hereby ratified and confirmed and is
acknowledged by the parties to be in full force and effect.

12. Miscellaneous. All references in the Lease and in this Amendment to the
“Lease” shall mean the Lease as modified by this Amendment. This Amendment shall
be deemed to have been executed and delivered within The Commonwealth of
Massachusetts, and the rights and obligations of Landlord and Tenant shall be
construed and enforced in accordance with, and governed by, the laws of The
Commonwealth of Massachusetts. This Amendment is binding upon and shall inure to
the benefit of the Landlord and Tenant and their permitted successors and
assigns. Each party has cooperated in the drafting and preparation of this
Amendment and, therefore, in any construction to be made of this Amendment, the
same shall not be construed against either party. This Amendment may be executed
in counterparts, and when both Landlord and Tenant have signed and delivered at
least one such counterpart, each counterpart shall be deemed an original, and,
when taken together with other signed counterparts, shall constitute one
Amendment, which shall be binding upon and effective as to Landlord and Tenant.
In case any one or more of the provisions contained in this Amendment shall for
any reason be held to be invalid, illegal or unenforceable in any respect, such
invalidity, illegality, or unenforceability shall not affect any other provision
of this Amendment, and this Amendment shall be construed as if such invalid,
illegal or unenforceable provision had never been contained herein. Neither the
submission of this instrument for signature, nor any draft thereof, shall
constitute an offer by Landlord to terminate the Lease. Neither party shall have
any obligation with respect to the matters set forth herein unless and until
such time as such party shall have executed and delivered this Amendment.

[Signature Page Follows]

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EXECUTED as a sealed Massachusetts instrument as of the date first written
above.

LANDLORD:

275 WYMAN LLC

By: /s/ Thomas M. Dusel
Manager

TENANT:

ALTUS PHARMACEUTICALS INC.

By: /s/ Georges Gemayel
Name:       Georges Gemayel      
Title: President/Assistant President

By: /s/ Thomas J. Phair, J.
Name:       Thomas J. Phair, Jr.      
Title: Treasurer/Assistant Treasurer

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