<PAGE>   1

                                                                  EXHIBIT 10.13


                   Sublease Agreement dated February 16, 1998
                  By and Between Vaxcel, Inc. and Oread, Inc.


<PAGE>   2


                                    SUBLEASE


         THIS SUBLEASE is made as of the 16th day of February, 1998, by and
between OREAD, INC., a Delaware corporation ("Oread"), and VAXCEL, INC., a
Delaware corporation ("Subtenant").

                                    RECITALS

         A. Oread is the tenant under that certain Lease dated February 16,
1998 (the "Prime Lease"), by and between Proceutics, Inc. ("Prime Landlord")
and Oread covering that certain building ("Building") located on the land
described in Exhibit A attached hereto and having the mailing address of 150
Technology Parkway, Norcross, Georgia 30092.

         B. Oread and Subtenant have agreed that Subtenant will sublease a
portion of the Building from Oread on the terms and conditions set forth
herein.

         NOW, THEREFORE, in consideration of the mutual covenants herein
contained and other good and valuable consideration, the receipt and
sufficiency of which is hereby acknowledged, the parties hereto agree as
follows:

         1. Sublease of Premises. Oread hereby subleases to Subtenant solely
for scientific research, storage and laboratory use, and Subtenant hereby rents
from Oread solely for scientific research, storage and laboratory uses a
portion of the Building consisting of approximately 1630 square feet as more
particularly shown on Exhibit B attached hereto and incorporated herein by this
reference ("Subleased Premises"). Subtenant shall take the Subleased Premises
in its "as is" condition.

         2. Prime Lease.

            (a) Except as otherwise provided herein, this Sublease shall be
upon the same terms and conditions as set forth in the Prime Lease, a copy of
which is attached hereto as Exhibit C and incorporated herein by this
reference. Subtenant shall observe and perform all of the covenants and
obligations of the Tenant under the Prime Lease with respect to the use,
operation and occupancy of the Subleased Premises. Without limiting the
generality of the foregoing, the following provisions of the Prime Lease shall
not apply to Subtenant: Sections 1, 2.1.3, 2.1.4, 2.1.5, 2.1.6, 2.1.7(b),
2.1.8, 2.1.10, 3, 5.1, 6.1, 9, and the indemnities in favor of Landlord set
forth in Sections 10.10, 20.1 and 39.1, except to the extent any such claim,
judgment, damages, penalties, fines, costs, liabilities or losses described in
such sections result from the acts, omissions or negligence of Subtenant or its
agents, employees, contractors or guests (the "Subtenant Indemnity
Obligations").

            (b) In those instances under the Prime Lease in which the Prime
Landlord


<PAGE>   3


thereunder has reserved certain rights with respect to the Demised Premises (as
defined in the Prime Lease), or with respect to the Tenant under the Prime
Lease, Oread shall be entitled to exercise all of such rights as against the
Subleased Premises and Subtenant with the same force and effect as if all such
rights of the Prime Landlord, as landlord under the Prime Lease, had been
expressly set forth in this Sublease.

             (c) With respect to obligations to be performed by the Prime
Landlord under the Prime Lease, Oread shall have no obligation with respect to
the performance of such obligations and shall have no liability to Subtenant by
reason of Prime Landlord's failure to perform the same; however, in the event
Prime Landlord shall breach such obligations, then, upon request by Subtenant,
Landlord agrees to cooperate with Tenant (at Tenant's cost and expense) to
cause Prime Landlord to perform such obligations. Tenant agrees to reimburse
Landlord upon demand, as additional rent, for any costs and expenses incurred
by Landlord at Tenant's direction to enforce compliance with the provisions of
the Prime Lease.

             (d) In the event of conflict between the Prime Lease and the
provisions of this Sublease, the applicable provision which is more restrictive
on Subtenant, or which imposes a greater obligation on Subtenant, shall
control.

             (e) Capitalized terms not otherwise defined herein shall have the
meaning ascribed to them in the Prime Lease.

         3.  Term. The term of this Sublease ("Sublease Term") shall commence on
February 16, 1998 ("Commencement Date") and shall expire on December 31, 1998,
unless sooner terminated in compliance with the terms of this Sublease.
Notwithstanding the foregoing, at any time prior to December 31, 1998,
Subtenant shall have the right to cancel this Sublease by giving to Oread at
least sixty (60) days' prior written notice of the intent to cancel. Said
notice shall specify the cancellation date ("Cancellation Date"), which date
shall not be on a day other than the last day of a month. Each of the parties
hereto shall be responsible for performance of all terms and conditions of this
Sublease which arise on or before the Cancellation Date.

         4.  Rent.

         (a) Subtenant shall pay to Oread as initial annual rent ("Sublease
Annual Rent") an amount equal to the greater of (i) Forty Eight Thousand Nine
Hundred Dollars ($48,900.00), or (ii) that sum which Oread must pay Landlord
pursuant to the Prime Lease as Rent on an annual basis attributable to that
portion of the Demised Premises designated hereunder as the Subleased Premises.
Subtenant shall pay to Oread the Sublease Annual Rent, without abatement,
deduction or offset, in lawful money of the United States of America, at the
address for Landlord set forth in Paragraph 13 of this Sublease. The initial
Sublease Annual Rent shall be paid on the first day of each month during the
Sublease Term in equal monthly installments of Four Thousand Seventy Five
Dollars ($4,075.00). The Sublease Annual Rent


                                       2
<PAGE>   4


is subject to adjustment as hereafter set forth.

         (b) The Sublease Annual Rent shall be increased effective each Rent
Adjustment Date under the Prime Lease by eighty cents ($.80) per square foot.

         (c) Within ten (10) days after Oread receives from Prime Landlord the
statement described in Section 7.2.1 of the Prime Lease showing the actual
Operating Expenses and Oread's Pro Rata Share of Building Operating Expenses
and Project Operating Expenses, Oread shall furnish to Subtenant a similar
statement showing the additional amount, if any, owed by Subtenant to Oread as
Sublease Annual Rent pursuant to Paragraph 4(a) above. If any additional amount
is owed by Subtenant to Oread, such amount shall be due and payable no later
than five (5) days after delivery to Subtenant of such statement. Subtenant's
obligation to pay any additional amount of Sublease Annual Rent due shall
survive the termination of this Sublease.

         (d) Any monthly installment of Sublease Annual Rent due for any period
less than a full month shall be prorated for such fractional month on the basis
of the actual number of days in the month.

         5.  Security Deposit.

         (a) On or before the Sublease Commencement Date, Subtenant shall
deposit with Oread a security deposit (together with all interest thereon, the
"Sublease Security Deposit") in the amount of Four Thousand Seventy Five
Dollars ($4,075.00), in cash, which Sublease Security Deposit shall be held by
Oread as security for the performance by Subtenant of all of the terms,
covenants and conditions of this Sublease to be kept and performed by Subtenant
during the Sublease Term. If a Default shall occur with respect to any
provision of this Sublease, including, without limitation, any provisions
relating to the payment of Sublease Annual Rent or any installment thereof,
Oread may (but shall not be required to) use, apply or retain all or any part
of the Sublease Security Deposit for the payment of any Sublease Annual Rent or
any other sum in Default, or to compensate Oread for any other loss or damage
which Oread may suffer by reason of Subtenant's default. If any portion of the
Sublease Security Deposit is so used or applied, Subtenant shall, upon demand
therefor, deposit cash with Oread in an amount sufficient to restore the
Sublease Security Deposit to its original amount, and Subtenant's failure to do
so shall be a material breach of this Sublease. The Sublease Security Deposit
shall be held in an interest bearing account separate from Oread's general
fund.

         (b) In the event of bankruptcy or other debtor-creditor proceedings
against Subtenant, the Sublease Security Deposit shall be deemed to be applied
first to the payment of Sublease Annual Rent and other charges due Oread for
all periods prior to the filing of such proceedings.

         (c) Oread shall deliver the Sublease Security Deposit, or any balance
thereof 


                                       3
<PAGE>   5

following application of any portion of the Sublease Security Deposit pursuant
to the provisions of Paragraph 5(a) above, to any purchaser of Oread's interest
in the Subleased Premises, and, upon such purchaser's written confirmation of
receipt of the Sublease Security Deposit and assumption of Oread's obligations
under this Sublease, Oread shall be discharged from any further liability with
respect to the Sublease Security Deposit. This provision also shall apply to
any subsequent transfers.

         (d) If Subtenant shall fully perform every provision of this Sublease
to be performed by Subtenant, the Sublease Security Deposit, or any balance
thereof following application of any portion of the Sublease Security Deposit
pursuant to the provisions of Paragraph 5(a) above, shall be returned to
Subtenant within thirty (30) days after the expiration or earlier termination
of this Sublease.

         6.  Indemnities. (a) All indemnity and hold harmless agreements
("Indemnities") made by Oread in favor of Prime Landlord under the Prime Lease
shall be deemed made by Subtenant in favor of Oread under this Sublease,
including, without limitation, the Indemnities contained in Sections 10.10,
20.1 and 39.1 of the Prime Lease, but only to the extent of the Subtenant
Indemnity Obligations. Nothing contained herein, however, shall be deemed to
negate any indemnity obligations of Oread in favor of the Prime Landlord under
the Prime Lease.

         (b) Oread hereby indemnifies and agrees to defend, hold and save
Subtenant harmless from and against any and all demands, claims, liabilities,
losses, costs, expenses, actions, causes of action, damages or judgments, and
all reasonable expenses actually incurred in investigating or resisting the
same (including, without limitation, reasonable attorneys' fees, charges and
disbursements actually incurred), for injury or death to person or injury to
property occurring within or about the Building, arising out of the use or
occupancy of the Building by Oread and its employees, agents or guests or a
breach or default by Oread in the performance of any of its obligations under
this Sublease, except to the extent caused by the acts, omissions or negligence
of Subtenant or its employees, agents, contractors or guests (provided that
nothing herein shall be deemed to affect the indemnity obligations of Subtenant
contained in Paragraph 6(a) above).

         7.  Parking. Subtenant shall not have the right to use the parking
facilities provided to Oread under the Prime Lease. Rather, Subtenant shall use
the parking facilities available to the occupants of the building located at
154 Technology Parkway, Norcross, Georgia.

         8.  Maintenance and Repair. Oread shall be responsible for all
maintenance with respect to the Subleased Premises in accordance with the
obligations of Tenant under the Prime Lease; provided, however, Subtenant shall
be responsible for the repair of any damage to the Subleased Premises or
Building which is caused by the activity of Subtenant, its employees, agents,
contractors, customers or invitees, and Subtenant also shall be responsible for
keeping the Subleased Premises clean and free of trash and debris. At the
conclusion of the term of the


                                       4
<PAGE>   6


Sublease, Subtenant shall be responsible for the repair of any damage to the
Subleased Premises or Building caused by the removal of Subtenant's property;
provided, however, that Subtenant shall not remove from the Subleased Premises
or Building any property which Oread would be prohibited from removing under
the Prime Lease. In addition, at the conclusion of the term of this Sublease,
Subtenant shall remove from the Subleased Premises and Building all radioactive
materials.

         9.  Insurance. Subtenant shall maintain the same type of insurance
Oread is required to maintain under the Prime Lease in accordance with Section
21 of the Prime Lease. Subtenant shall provide Oread with a certificate
evidencing the required insurance, which certificate shall show Oread and Prime
Landlord as additional insureds.

         10. Default. The terms and provisions of Section 24 of the Prime Lease
shall determine and govern any default by Subtenant under this Sublease. All
late charges, default interest and other charges which Prime Landlord has the
right to recover under the Prime Lease from Tenant can be recovered by Oread
from Subtenant under this Sublease, with such amounts being calculated with
respect to the rent payable by Subtenant for the Subleased Premises only.

         11. Assignment or Subletting. Subtenant shall not, either voluntarily
or by operation of law, directly or indirectly, sell, hypothecate, assign,
pledge, encumber or otherwise transfer this Lease or sublet the Subleased
Premises or any part thereof without the prior written consent of Oread and
Prime Landlord in each instance, which consent can be withheld in the sole and
absolute discretion of Oread and/or Prime Landlord.

         12. Services by Oread. Subtenant agrees that Oread shall have no
responsibility for the provision of any service which is the responsibility of
Prime Landlord under the Prime Lease, and that Subtenant shall look solely to
Prime Landlord for such services. Subtenant further agrees that Oread has not
agreed to provide any other service or assistance to Subtenant in connection
with this Sublease, except as specifically set forth herein.

         13. Notices. All notices and demands which are required to be given
shall be in writing and shall be given in the same manner required by Section
40.11 of the Prime Lease at the addresses of the respective parties set forth
below:


                                       5
<PAGE>   7




         Oread:                     Oread, Inc.
                                    1501 Wakarusa Drive
                                    Lawrence, Kansas 66047
                                    Attention:  Legal Department

         Subtenant:                 Vaxcel, Inc.
                                    c/o CytRx Corporation
                                    154 Technology Parkway
                                    Norcross, Georgia 30092
                                    Attention: Jack Luchese

         Prime Landlord:            At the address set forth in
                                    the Prime Lease

         14. Miscellaneous.

         (a) This Sublease, together with any exhibits hereto, constitutes the
entire agreement between the parties with respect to the subject matter hereof
and supersedes any prior representations and understandings. This Sublease may
not be amended or modified except in a writing executed by both parties, and
subject to any required consent of the Prime Landlord.

         (b) The paragraph captions used in this Sublease are for convenience
and reference only, and the words contained therein shall in no way be held to
explain, modify, amplify or aid in the interpretation, construction or meaning
of the provisions of this Sublease.

         (c) Submission of this instrument for examination or signature by
Subtenant does not constitute a reservation of or option for lease, and this
Sublease is not effective as a lease or otherwise until execution by and
delivery to both Landlord and Tenant.

         (d) Time is of the essence with respect to the performance of every
provision of this Sublease in which time of performance is a factor.

         (e) Each provision of this Sublease performable by Subtenant shall be
deemed both a covenant and a condition.

         (f) In the event any of the provisions of this Sublease shall at any
time be held by a court of competent jurisdiction to be illegal, invalid or
unenforceable for any reason, such illegality, invalidity or unenforceability
shall not affect the remaining provisions of this Sublease, and this Sublease
shall be construed and enforced as if all such illegal, invalid or
unenforceable provisions had never been inserted herein.


                                       6
<PAGE>   8


         (g) The language in all parts of this Sublease (together with the
Prime Lease) shall be in all cases construed as a whole according to its fair
meaning and not strictly for or against either Oread or Subtenant.

         (h) Whenever herein the singular number is used, the same shall
include the plural and vice versa, and the neuter gender shall include the
feminine and masculine genders.

         (i) Each of the covenants, conditions and agreements herein contained
shall inure to the benefit of and shall apply to and be binding upon the
parties hereto and their respective successors and assigns or any person who
may come into possession of the Subleased Premises or any part thereof in any
manner whatsoever. Nothing in this Paragraph 14(i), however, shall in any way
alter the prohibition against assignment or subletting contained in this
Sublease.

         (j) This Sublease shall be governed by, construed and enforced in
accordance with the laws of the State of Georgia.

         (k) All obligations of Oread and Subtenant which by their nature
involve performance, in any particular, after the end of the Sublease Term or
which cannot be ascertained to have been fully performed until after the end of
the Sublease Term shall survive the expiration or sooner termination of this
Sublease.

         (l) Oread and Subtenant each represent and warrant to the other that
the person or entity signing this Sublease on behalf of such party is duly
authorized to execute and deliver this Sublease and to legally bind the party
on whose behalf this Sublease is signed to all of the terms, covenants and
conditions contained herein. Subtenant represents and warrants that it is and
shall remain during the Sublease Term in good standing under the laws of the
state in which it was organized and in the state in which the Subleased
Premises are located.

         15. WAIVER OF JURY TRIAL AND COUNTERCLAIMS.

         THE PARTIES HERETO SHALL AND THEY HEREBY DO WAIVE TRIAL BY JURY IN ANY
ACTION, PROCEEDING OR COUNTERCLAIM BROUGHT BY EITHER OF THE PARTIES HERETO
AGAINST THE OTHER ON ANY MATTERS WHATSOEVER ARISING OUT OF OR IN ANY WAY
CONNECTED WITH THIS SUBLEASE, THE RELATIONSHIP OF OREAD AND SUBTENANT,
SUBTENANT'S USE OR OCCUPANCY OF THE SUBLEASED PREMISES OR ANY CLAIM OF INJURY
OR DAMAGE.


                                       7
<PAGE>   9


         IN WITNESS WHEREOF, the parties hereto have executed this Lease to be
effective as of the date first above written.

LANDLORD:                        OREAD, INC.,
                                     a Delaware corporation


                                     By:
                                        ---------------------------------------

                                     Printed Name:
                                                  -----------------------------

                                     Title:
                                           ------------------------------------


SUBTENANT:                           VAXCEL, INC.,
                                     a Delaware corporation

                                     By:
                                        ---------------------------------------

                                     Printed Name:
                                                  -----------------------------

                                     Title:
                                           ------------------------------------


                              CONSENT TO SUBLEASE

         The undersigned, as Prime Landlord under the Prime Lease, hereby
consents to the subletting of the Subleased Premises to Subtenant under the
terms and conditions contained in this Sublease.


                                     PROCEUTICS, INC.,
                                     a Delaware corporation

                                     By:
                                        ---------------------------------------

                                     Printed Name:
                                                  -----------------------------

                                     Title:
                                           ------------------------------------


                                       8
<PAGE>   10


                                                                      EXHIBIT A

                                     [LAND]


<PAGE>   11



                                                                      EXHIBIT B

                              [SUBLEASED PREMISES]


<PAGE>   12



                                                                      EXHIBIT C

                                 [PRIME LEASE]