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                                                                   EXHIBIT 10.37

                                 March 12, 1997



Ribozyme Pharmaceuticals, Inc.
2950 Wilderness Place
Boulder, CO  80301

Attn:    Mr. Larry Bullock

         Re:     LETTER AGREEMENT CONCERNING EXTENSION OF CURRENT LEASE

Dear Mr. Bullock:

         The parties to this letter agreement are AERO-TECH INVESTMENTS, a
Colorado general partnership ("Aero-Tech") and Ribozyme Pharmaceuticals, Inc.,
a Delaware corporation ("RPI").  This letter also refers to a related party
known as Wilderness Place Holdings LLC, a Colorado limited liability company
("WPH").

         RPI and Aero-Tech are parties to that certain Lease dated May 20, 1992
consisting of 29 pages, which has attached thereto a "Lease Information
Summary" of seven pages, an Exhibit A which is a floor plan identifying the
demised premises, an Exhibit B which is a description of certain improvements
to be installed as more particularly described in the Lease, an Exhibit C
entitled "Building Rules and Regulations" of three pages, an Exhibit C-1
entitled "Special Rules and Regulations Regarding Animals" of one page, and a
one-page Exhibit D entitled "High Voltage Electrical Equipment of Tenant"
(hereinafter referred to as the "Lease").  The Lease has been amended by that
certain "Amendment of Lease" dated March 23, 1995 and that certain "Amendment
of Lease" dated June 23, 1995.  The Lease has also been amended by that certain
Agreement between RPI and Aero-Tech dated March 27, 1995 ("Side Agreement").
The Lease, as amended by each of the above-referenced documents, is hereinafter
referred to as the "Amended Lease."  The Amended Lease was assigned by RPI, as
the tenant thereunder, to WPH.  WPH, in turn, then subleased the Leased
Premises back to RPI.  This transaction was accomplished by that certain Lease
and Sublease Agreement dated April 4, 1995 between WPH and RPI.  Aero-Tech
consented to the subleasing transaction described above in that certain
"Consent to Assignment and 'Lease and Sublease'; and Amendment of Lease" by and
between Aero-Tech, RPI and WPH dated April 4, 1995.  As referred to herein, the
"Amended Lease" shall specifically include those amendments contained in the
above-referenced Consent.  The above- referenced Consent executed by Aero-Tech
shall hereinafter be referred to as the "Consent Agreement."  All other
capitalized terms used in this letter agreement, but not otherwise defined
herein, shall have the meanings ascribed to such terms by the Amended Lease
and/or the Consent Agreement.





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         Aero-Tech and RPI now desire to provide for further amendment of the
Amended Lease with the approval of WPH.  This letter agreement is entered into
by Aero-Tech, RPI and WPH to provide for certain amendments to the terms and
conditions of the Amended Lease as set forth herein.

         NOW, THEREFORE, in consideration of the premises, the respective
promises and covenants set forth herein, the consideration currently set forth
in the Amended Lease and other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, Aero-Tech, RPI and WPH agree as
follows:

         1.      Exercise of First Option to Extend.  Notwithstanding any term,
condition or provision contained within the Amended Lease, WPH shall be and is
hereby deemed to have extended the Lease pursuant to that certain Option to
Extend contained in Section 13(a) of the Lease Information Summary attached to
the Amended Lease.  As a result of the exercise of this option by WPH, the Term
of the Amended Lease shall be extended and the Term Expiration Date thereof
shall be and is hereby amended to read "June 30, 2002."

         2.      Exercise of Second Option to Extend.  The Side Agreement
between RPI and Aero-Tech contains (in Section 2 thereof), an option for RPI to
extend the Amended Lease for a "Second Extended Term."  Notwithstanding any
term or provision contained within the Amended Lease, RPI has and shall be
considered hereby to have exercised, in writing, RPI's option to extend the
Amended Lease for the Second Extended Term.  RPI acknowledges that RPI shall be
bound by all terms and conditions of the Amended Lease with respect to the
Second Extended Term as set forth in the Side Agreement.  RPI further
acknowledges that, in accordance with the specific terms and conditions of the
Side Agreement, no uncured event of default, and no event or condition which,
with the giving of notice or the passage of time or both, would constitute an
event or condition of default, shall exist under the Amended Lease upon the
date of commencement of the Second Extended Term.  If such an event of default
exists at any time within 6 months prior to the date of commencement of the
Second Extended Term, Aero-Tech shall not be required to allow RPI to continue
occupancy of the Leased Premises during the Second Extended Term and the
Amended Lease shall then expire and terminate under its own terms and
conditions.  (As used in the previous sentence, the term "Amended Lease" shall
be deemed  to include any and all amendments to the original Lease, including
those amendments set forth in this letter agreement and any other Lease
amendments executed by the parties to the Lease or the Amended Lease prior to
the commencement of the Second Extended Term.)  Notwithstanding any term or
condition contained in the Side Agreement and/or the Amended Lease, the Base
Rent for the Second Extended Term shall be equal to the greater of the
then-current monthly rent under the terms and conditions of the Amended Lease
or the Market Rent as defined in the Side Agreement.  Base Rent shall continue
to be escalated by the CPI Index pursuant to the terms and conditions set forth
in the Amended Lease.







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         3.      WPH Reassignment.  RPI hereby agrees to satisfy, in full, its
financial obligations to WPH and to cause WPH to assign the Amended Lease to
RPI (making RPI the sole and only tenant under the terms and conditions of the
Amended Lease) on or before March 31, 1999.  WPH, in turn, agrees, upon full
satisfaction of RPI's financial obligations to WPH, to fully assign the Amended
Lease to RPI in accordance with the terms and conditions contained in the Lease
and Sublease Agreement between RPI and WPH.  RPI hereby acknowledges that the
terms and conditions set forth in this paragraph of the letter agreement are
material consideration for and a primary inducement of Aero-Tech to enter into
the terms and conditions of this letter agreement.  Default by RPI hereunder
shall specifically exclude, at the option of Aero-Tech, RPI's continued
occupancy of the Leased Premises during the Second Extended Term and shall be
considered a material default by RPI under the terms and conditions of the
Amended Lease.

         RPI's Agreement to Leave Certain Lab Fixtures and Equipment in the
Leased Premises Upon any Vacation Thereof.  Section 5.03 of the Amended Lease
states that all additions to or improvements of the Leased Premises, whether of
Building Standard Improvements or Tenant Extra Improvements, shall become the
property of Landlord upon installation and shall be surrendered to Landlord
upon termination of the Amended Lease by lapse of time or otherwise, subject to
Tenant's rights of removal with respect thereto as provided in Section 5.08 of
the Amended Lease, unless Landlord has otherwise agreed in writing to allow
some or all of the Tenant Extra Improvements to remain the property of Tenant
prior to installation thereof.  Section 5.08 of the Amended Lease, among other
things, allows Tenant to remove "movable equipment or furniture" owned by
Tenant upon the expiration or other termination of the Amended Lease if Tenant
repairs all damage caused to the Leased Premises or the Project by such
removal.  RPI and Aero-Tech hereby agree that if Aero- Tech elects, any and all
of the following items shall be and are hereby considered to be the "property
of Landlord" and shall specifically not be considered to be "movable equipment
or furniture owned by Tenant" all laboratory structures, fixtures and items
necessary for the Leased Premises to remain a usable, operational lab facility
including but not limited to all lab fixtures, air handling equipment, all roof
installations, exhaust fans, generators, boilers, sinks, fume hoods, casements,
cabinetry, circulating fans and associated equipment. "Moveable equipment or
furniture owned by Tenant" shall include but not be limited to office furniture
and equipment, portable equipment, NMR, synthisizers, portable water
purification equipment, laminar flow hoods, portable manufacturing equipment,
computer equipment and other portable personal property of the business.

Each of the above-referenced " Property of Landlord" items shall at the sole
option of the Landlord become the property of Landlord and shall be surrendered
to Landlord upon the termination or other expiration of this Amended Lease by
lapse of time or otherwise.  RPI hereby agrees that all items surrendered to
Landlord pursuant to the terms and conditions of the Amended Lease shall be
free and clear of all liens or, in the alternative, RPI shall, at the time of
such expiration or other termination, make arrangements satisfactory to
Aero-Tech to service any outstanding debt with respect to such items.  Each of
the terms and conditions within the Amended Lease referring to the
above-referenced items shall be and is hereby amended as more particularly set
forth herein. Any term or condition contained in






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paragraph IV of this letter, which are inconsistent with the existing
conditions of Section 5.03 of the Ammended Lease shall be deemed to control.

         4.      RPI's Waiver of Rights to Take Additional Space.  RPI hereby
waives all existing rights of RPI to negotiate to take more space contained
within the Amended Lease; including but not limited to those rights set forth
in Section 15 of the Lease Information Summary and in Section 12 of the Consent
Agreement. RPI hereby acknowledges and agrees that RPI has no current rights,
after the effective date of this letter agreement, to negotiate to take more
space anywhere on the Project 5Intentionally Ommitted

         5.      Binding Effect.  Aero-Tech and RPI hereby agree that the terms
and conditions contained within this letter agreement shall be effective
immediately and shall be binding upon and inure to the benefit of both
Aero-Tech and RPI whether or not this letter agreement is executed by WPH.  In
the event that this letter agreement is not executed (for any reason) by WPH,
RPI and Aero-Tech hereby agree that the terms and conditions contained herein
shall bind only Aero-Tech and RPI and shall be effective whether or not RPI is
assigned the Amended Lease by WPH or, in the alternative, RPI, under any manner
or circumstances, becoming the sole tenant pursuant to the Amended Lease in
accordance with the terms hereof.  If WPH does not execute this letter
agreement, the terms and conditions hereof shall become binding upon Aero-Tech
and RPI contemporaneously with any act or action causing RPI to become the sole
tenant under the terms and conditions of the Amended Lease.

         6.      Miscellaneous.

                 (a)      Each reference to the term "Lease" and/or "Amended
Lease" contained in any document referenced herein shall be and is hereby
modified to include the Amended Lease, as amended hereby.

                 (b)      Except as expressly modified or amended herein, the
terms and conditions of the Amended Lease shall remain unmodified and in full
force and effect, and are hereby ratified and reconfirmed by the parties
hereto.

                 (c)      The terms and conditions contained in this letter
agreement shall be construed in accordance with the laws of the State of
Colorado.

                 (d)      This letter agreement may be executed in
counterparts, each of which when taken together shall constitute the original
instrument.  Facsimile signatures shall be acceptable to bind any party hereto.





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         If you agree to be bound by and acknowledge the terms and conditions
contained within this letter agreement, please indicate your acceptance and
acknowledgment thereof in the signature blocks provided below.  After
execution, please immediately forward conformed originals of this letter
agreement to Aero-Tech via facsimile transmission and personal delivery.

                                        Very truly yours,

                                        Landlord:

                                        AERO-TECH INVESTMENTS


                                        By: /s/ Alan Clamon
                                            ---------------
                                        Name Printed
                                        Title: Alan Clamon, Partner
                                               --------------------

         Agreed to, acknowledged and accepted this 13 day of
 March, 1997.

                                        Tenant:

                                        RIBOZYME PHARMACEUTICALS, INC.



(SEAL)                                  By:  /s/ Lawrence Bullock
                                             -----------------------

                                        Name Printed: Lawrence E. Bullock
                                                      -------------------

                                        Title: V.P. Finance & Admin, CFO
                                               -------------------------


                                        WILDERNESS PLACE HOLDINGS LLC


                                        By:_______________________________

                                        Name Printed:______________________

                                        Title:______________________________