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Exhibit 4.11
 Joint Venture Agreement
  between
    
    andMicromet GmbH
    
    tgb Technologie Beteiligungs-Am Klopferspitz 19
    
    Gesellschaft mbH derDeutschen Ausgleichsbank82152 Martinsried
    
    53179 Bonnhereinafter: Technology Corporation (TC) -
    
    - Silent Partner; hereinafter: tgb
  *** DM 513,274.00 ***
 (I n words: five hundred thirteen thousand two hundred seventy-four Deutschmarks)
 Preamble
 Within the framework of the DtA technology investment program, tgbshall assume investments for
financing of projects in the start-up phase, of innovation-related projects, and of exit financing
projects as defined by the investment principles of this program, which are an integral part of
this Agreement.
 §1
 Corporate Purpose
 1.
    
    The TC registered with the Municipal Court (Amtsgericht) Munich under number B105424 engages
in a trade pursuant to the Articles of Incorporation dated December 16,1993 with the purpose
of:
 Implementation of biomedical contract research within the scope of development of products for
diagnosis and treatment of human diseases
 2.
    
    Within the scope of this corporate purpose,
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the TC engages in bringing previous product developments for treatment of minimally residual
carcinoma into the clinical phase, supplemented by the development of a product for cancer of the
lymphatic system.
 § 2
 Contribution
 1.
    
    tbgshall assume a contribution in the amount of DM 513,274.00, exclusively for financing of
the innovation-related project described in § 1 para. 2 and based on the information furnished
by the TC in the investment solicitation dated August 6, 1998, if the TC provides evidence of
the following joint venture agreements:
 ð
    
    Joint venture agreement in the amount of DM 930,159.00 withAtlas Venture Germany B.V.PO Box 5225NL- 1410 NaardenThe Netherlands(hereinafter: Investor, even in case of more than one investor)and the Investor with whom tbghas executed a Cooperation Agreement.ð
    
    Direct debit authority for collection of all due fixed compensation through tbgð
    
    Investment by additional investors in the amount of at least DM 6,478,536.00
 2.
    
    tbgs contribution shall be appropriated for co-financing of the project-specific planning
listed in Appendix I, which an integral part of this Joint Venture Agreement.
 3.
    
    The TC can call up the contribution after start-up of the corporation (cf. § 3 para. 1)
provided that its prompt utilization in accordance with its specified purpose, a proportionate
use of funds with the other financing funds listed in Appendix I, and the total financing of
the innovation-related project are guaranteed.
 A confirmation of the requirements for the call shall be attached to the call by the Investor.
 4.
    
    This Agreement shall be terminated if the contribution has not been called, at least in part,
no later than May 31,1999.5.
    
    tbgshall withhold a processing fee in the amount of 1.00% of the total contribution agreed
on in this Agreement for the first partial call.6.
    
    tbgs contribution shall be kept in a special deposit account to be handled by the TC.
Withdrawals by tbgfrom this account are not permitted.
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§3
 Commencement and Duration of the Corporation
 1.
    
    The Silent Partnership shall commence as soon as this Agreement has been executed by both
parties.
 2.
    
    The Silent Partnership is limited in time until December 31, 2008.
 3.
    
    Upon termination of the partnership, tbgs contribution and any profit shares not paid out
shall be due to tbg.
 4.
    
    Insofar as the funds granted by the Investor have been paid back prior to December 31, 2008,
tgbs contribution shall be due for repayment at the same time and to the same extent. tbgis
entitled to request final compensation pursuant to § 8 para. 4 mutatis mutandis for that
portion of its contribution, which is due for early repayment.
 §4
 Management
 1.
    
    tbgshall not participate in the management of the TC, except as otherwise provided herein.
 2.
    
    The TC is required to obtain tbgs consent for
 a)
    
    Each change of the Articles of Incorporation, including but not limited to any change
in the corporate purpose, acceptance of new partners, or agreement on new investments;b)
    
    Appointment or dismissal of managers of the TC or changes to the Management Employment
Agreement;c)
    
    Execution, amendments, and termination of contracts with respect to the granting or
acquisition of licenses, trademarks, or know-how (except with respect to the day-to-day
software business), patents, utility and design patents, insofar as they concern the
innovation-related project developed using tbgs investment;d)
    
    Execution, amendments, and termination of major distribution contracts;e)
    
    Partial or complete site relocation, or leasing, disposal, or shut-down thereof;f)
    
    Execution and termination of controlling agreements and profit-and-loss transfer agreements;g)
    
    Abandonment of or essential changes in the innovation-related project described in § 1 para.
2;h)
    
    Acceptance by tbgof obligations, insofar as these are not part of project financing,
for investments that are in excess of DM 100,000 or for leasing or rental agreements or
leases in excess of a monthly amount of DM 10,000.
 3.
    
    Consents pursuant to § 4 para. 2 shall be obtained directly from tbg.Insofar as tbgdoes not state in writing the refusal to grant consent pursuant to § 4 para. 2
within a period of 14 days after receipt of notice of measures requiring approval, consent shall
be deemed granted.
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§5
 Information and Control Rights
 1.
    
    The TC shall inform tbgevery six months, no later than March 31 and September 30
respectively of each year regarding the economic situation of the TC and with respect to the
innovation-related project described in § 1 para. 2, as long as tbgdoes not waive these
reports because the Investor is also concurrently performing the control review of the TC for
tbg. tbgshall also receive from the TC a brief, monthly state of affairs summary report in
accordance with the attached Appendix IIand, at the end of the fiscal year, a properly
updated business plan for the following year.2.
    
    Regardless of whether the Investor is performing the control review of the TC concurrently
for tbg, the TC shall inform tbgdirectly and in a timely manner with respect to all measures
extending beyond standard business procedures.3.
    
    Additionally, tbgis entitled to control rights pursuant to § 716 of the German Civil Code
(BGB). This also applies after termination of the corporation to the extent necessary to
review the liquidation balance.tbgis also entitled to access all of the TCs documents with reference to the innovation-related
project described in § 1 para. 2. tbgcan use third-party services when exercising its control
rights.4.
    
    The Federal Audit Office (Bundesrechnungshof) is entitled to audit the TC pursuant to § 91 of
the Federal Budget Code (BHO). The TC shall furnish all documents that the Federal Audit
Office deems necessary to the Federal Audit Office and tbgfor audit purposes and shall
furnish all appropriate information.
 § 6
 Advisory Board
 tbgcan request constitution of an Advisory Board at any time. tbgshall participate in this
Advisory Board commensurately with the amount of its contribution. The Advisory Board shall advise
the TC with respect to economic and technical aspects, including but not limited to with respect to
the project described in § 1 para. 2. The Advisory Board shall have the same information and
control rights that tbgis entitled to under this Agreement.
 § 7
 Business Year; Annual Financial Statement
 1.
    
    The fiscal year of the Silent Partnership shall correspond to that of the TC (investment
year). The TCs fiscal year shall end on December 31 of each year.
 2.
    
    The TC shall draw up its annual financial statement (balance sheet, statement of income,
notes) in compliance with §§ 238  289 of the German Commercial Code (HGB) within six months
after the end of the fiscal year and shall furnish an original, signed copy of this financial
statement to tbgwith the attestation of an auditor or certified accountant.
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§8
 Profit and Loss Sharing
 1.
    
    For its contribution, tbgshall receive a minimum compensation independent of the TCs net
income in the amount of 7.00% per annum. Such compensation shall be due in arrears every six
months as of May 31 and November 30 of each year.2.
    
    Additionally, tbgshall receive 9.00% of the annual net income generated after call up of the
contribution.For a period in which tbgholds more than one investment in the TC, tbgshall receive only 9.00%
for all investments, aside from the respective minimum compensations from the generated annual net
income.If additional capital is put into the TC within the scope of additional financing rounds, tbgshall
adjust its profit share to the capital conditions valid at that time.This profit share is payable within 2 weeks upon approval of the annual financial statement (§ 7
para. 2).3.
    
    The annual net income before recognition of tbgs profit share is applicable for the
calculation as defined by para. 2.
 a)
    
    To be added to the annual net income:
 -
    
    Taxes on income and managers royalties, if any, to the extent that
they have reduced the posted annual net income;-
    
    Extraordinary expenditures, insofar as they originate from business
events prior to commencement of the Silent Partnership;-
    
    Losses from disposal or destruction of fixed assets, insofar as these
were existent at the time of commencement of the corporation.b)
    
    To be deducted from the annual net income:-
    
    Amounts from the liquidation of tax-free reserves that were established prior to commencement of the Silent Partnership;-
    
    Extraordinary earnings insofar as they are based on business events that took place prior to commencement of the Silent
Partnership;-
    
    Public subsidies, allowances, and appropriations, insofar as they affect net income;-
    
    Earnings from disposals of fixed assets, insofar as these already existed at the time of commencement of the corporation.c)
    
    In the year of the call up of the investment, the annual net income for the calculation of
the profit share as defined by para. 2 shall be deemed as having accrued evenly during the
course of the year.
 4.
    
    At the end of the investment period, tbgis entitled to a one-time compensation of 35% of the
investment amount plus 7% of the investment amount for each year after the end of the fifth
full investment year (final compensation). The annually paid profit sharing as defined by § 8
para. 2 shall be set off against the final compensation to be paid. If the sum total of the
profit share exceeds the final compensation, no monies shall be reimbursed.
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5.
    
    If shares of the TC (if applicable, after conversion of the TC into a stock corporation)
are to be admitted to trading on a stock exchange and the TC has executed a letter of
engagement or a comparable document with an underwriting member bank,
tbgcan request that shares in the TC be issued or existing shares be transferred to tbgagainst transfer or
assignment of the entitlement to payment of the final compensation pursuant to para. 4. tbg
shall direct the request to the TC in writing. The amount of the claim is calculated based on
the period from execution of the Joint Venture Agreement until receipt of the request by the
TC in accordance with sentence 1. The number of shares to be issued or transferred to tbgis
calculated by dividing the amount of final compensation by the exercised amount. The exercised
amount is determined from the average of the expected or final established minimum or maximum
amount of the price spread at the time of the initial public offering for one share of the TC;
however, the exercised amount shall not exceed 90% of the highest amount of the price spread.
Insofar as payments based on profit-dependent compensation to tbgare set off against
entitlement to the final compensation, the previous stipulations are applicable mutatis
mutandis to the entitlement to final compensation reduced by this amount.The TC shall inform tbgpromptly in writing if an initial public offering is planned and if a
letter of engagement or a similar document has been executed. tbgshall exercise its right to
convert the entitlement to final compensation into shares in the TC within four weeks after receipt
of the TCs notification. The parties shall effect all acts and make all statements necessary to
cause the issuance or transfer of shares to tbg. The TC shall assert its influence over its
shareholders so that they shall take the necessary actions and make the necessary
declarationsincluding but not limited to with respect to a possible capital increase. If, prior to
the completion of the investment in the TC by tbgon the basis of the exercise of the option, the
listing of the TCs shares for trading on a stock exchange is no longer being pursued, tbgcan
demand that the option be deemed not exercised, to the extent that actions completed and
declarations given up to the time of the appropriate statement can still be rescinded; in this
case, tbgs option privilege shall continue to exist and can be exercised again if the previously
stated requirements have been met.6.
    
    tbgshall not participate in the TCs losses.
 §9
 Taxes
 The TC shall take care of payment of the legally required capital gains tax plus solidarity
surcharge with respect to the compensation for the silent contribution, shall withhold capital
gains tax and the solidarity surcharge from the payments to tbg, and shall pay them to the
appropriate Tax Office as soon as they become due. Upon payment thereof, the TC shall within 2
months after the payments to the Tax Office became due furnish, on the forms provided by tbg,
attestations as defined by § 45a para.2 of the Income Tax Act (EStG).
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§10
 Liquidation of the Silent Partnership
 1.
    
    In case of liquidation of the TC, the Silent Partnership shall be liquidated. In this case,
the silent contribution shall be repaid.2.
    
    In this case, § 8 para. 4 shall apply.
 §11
 Termination
 1.
    
    The TC is entitled to redeem tbgs investment in whole or in part with a period of notice of
3 months on June 30 or December 31 of each year. If such redemption is made before the end of
the fifth full investment year, tbgs contribution shall be repaid with a premium of 35%. The
provision under § 8 para. 4 applies as of the start of the sixth investment year. tbgcan
waive payment of the premium if the termination was made due to abandonment of the
innovation-related project developed as defined in § 1 para. 2.
 2.
    
    Additionally, the Silent Partnership can be terminated in writing by either partner for due
cause without a period of notification. Insofar as the contribution has not yet been made in
whole or in part, tbgshall be free of its contribution obligation at the time the Silent
Partnership is terminated.tbgis entitled to terminate the Agreement for due cause for reasons that include but are not
limited to the following:
 a)
    
    If the TC furnished incorrect information in the investment solicitation;b)
    
    If it becomes apparent that the requirements for the granting or continuation of the joint
venture were not met or that the requirements for the continuation of the joint venture no
longer exist, including but not limited to if the innovation-related project cannot be
implemented as defined in § 1 para. 2, or is abandoned by the TC, or is significantly amended.
If the innovation-related project as described in § 1 para. 2 proves to be technically
unfeasible or cannot be implemented for economic reasons, tbgcan waive repayment of the
investment in whole or in part, if such an action enables the TCs continued existence;c)
    
    If bills of exchange accepted by the TC are protested, the TC stops payments, a bankruptcy
petition has been filed, or insolvency has been determined in any other way;d)
    
    If the managers with the appropriate expertise employed by the TC at the time of execution of
the Joint Venture Agreement relative to the Silent Partnership no longer work at the corporate
management level of the TC;e)
    
    If one of the actions stipulated in § 4 para. 2 was implemented without prior consent of tbg.
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§12
 Due Payments
 In the event of payment default, due payments shall accrue interest in the amount of 4% per annum
until they have been received by tbg.
 §13
 Miscellaneous provisions
 1.
    
    Amendments and additions to this Agreement shall be in writing. No oral ancillary agreements
to this Agreement have been made.2.
    
    If a provision in this Agreement should be or become invalid, the remaining provisions shall
remain unaffected. The TC and tbgare obligated to replace invalid provisions with such
provisions that are valid and that correspond to the greatest extent possible to the spirit
and economic purpose of the invalid provision.3.
    
    Bonn is agreed upon as venue for any and all disputes arising from this Agreement and its
implementation.
 Bonn,
dated: March 2, 1999
Technologie-Beteiligungs-
    
    Martinsried, dated:
February 15, 1999
Micromet GmbHGesellschaft mbH der-s- Micromet GmbHDeutschen Ausgleichsbank
    
    [signature][signature]      [signature]
   tbg
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Project-Specific Planning
 Appendix I
 Projected time period: September 30, 1998 until December 31, 2000
 
 Project-Specific
Expenditures
    
    
    Amount without value-added taxI. Applied research and developmentI. Investments shown in the intangible fixed assets1.1Lab devices and equipment
    
    
    
    DM
    104,759.001.2 Machinery and equipment for production of prototype
    
    
    
    DM
    0.001.3 Other
    
    
    
    DM
    0.002. Non-investive research and development expenses2.1 Personnel
    
    
    
    DM
    1,031,344.002.2 Material
    
    
    
    DM
    362,398.002.3 Third-party services (contract award/ consulting)
    
    
    
    DM
    59,953.002.4 Patents and permits
    
    
    
    DM
    81,252.002.5 Travel expenses
    
    
    
    DM
    86,931.002.6 Other
    
    
    
    DM
    415,567.00II. Investments for market launch
    
    
    
    DM
    0.00Total
    
    
    
    DM
    2,142,204.00
 Project-Specific Financing
    
    
    
    Amount1. Equity capital
    
    
    
    DM
    318,065.001.1 1.2 2. Investment capital2.1 of tbg
    
    
    
    DM
    513,274.002.2 of lead investors
    
    
    
    DM
    930,159.002.3 other participating parties
    
    
    
    DM
    238,713.003. Public funding3.1 subsidies, allowances, appropriations
    
    
    
    DM
    0.003.2 Other
    
    
    
    DM
    141,933.004. Outside capital4.1 from bank
    
    
    
    DM
    0.004.2 Other
    
    
    
    DM
    0.00Total
    
    
    
    DM
    2,142,204.00
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Fax-No.: 0228/ 831 24 93 Esko Stahl
 Appendix II
 Brief Statement of Affairs Summary
 
  Brief statement of affairs summary for the month of *           199
 Balance inthousands of DMSales revenueMaterial expensesPersonnel expensesOther expensesProvisional operating resultCurrent volume of ordersCredit frameworkOf which utilizedCurrent number of employees (please
state temporary employees in percent)
  Noteworthy events during the past month:
 Assessment of Future Development
 o o o o o
  
 Corporate Stamp and Signature(s)
 
 Always due no later than at the end of the following month
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