Our management's discussion and analysis of our financial condition and results of operations are based upon our unaudited condensed consolidated financial statements included in this Quarterly Report on Form 10-Q, which have been prepared by us in accordance with accounting principles generally accepted in the United States, or U.S. GAAP, and with Regulation S-X promulgated under the Securities Exchange Act of 1934, as amended, or Exchange Act. This discussion and analysis is intended to assist in providing an understanding of our financial condition, changes in financial condition and results of operations and should be read in conjunction with these unaudited condensed consolidated financial statements and the notes thereto included elsewhere in this Quarterly Report on Form 10-Q and the discussion and analysis included in our Annual Report on Form 10-K for the year ended December 31, 2021, filed with the SEC on February 28, 2022 (the "Annual Report on Form 10-K"). Some of the information contained in this discussion and analysis or set forth elsewhere in this Quarterly Report on Form 10-Q, including information with respect to our plans and strategy for our business, includes forward-looking statements that involve risks and uncertainties. As a result of many factors, including those factors set forth in Part II, Item 1A. Risk Factors of this Quarterly Report on Form 10-Q, our actual results could differ materially from the results described in or implied by the forward-looking statements contained in the following discussion and analysis.



Overview

General

We are a clinical-stage oncology company developing innovative antibody therapeutics. Our pipeline of full-length human multispecific antibody candidates are generated from our proprietary technology platforms, which are able to generate a diverse array of antibody binding domains, or Fabs, against virtually any target. Each antibody binding domain consists of a target-specific heavy chain paired with a common light chain. Multiple binding domains can be combined to produce novel multispecific antibodies that bind to a wide range of targets and display novel and innovative biology. These platforms, referred to as Biclonics® and Triclonics®, allow us to generate large numbers of diverse panels of bispecific and trispecific antibodies, respectively, which can then be functionally screened in large-scale cell-based assays to identify those unique molecules that possess novel biology, which we believe are best suited for a given therapeutic application. Further, by binding to multiple targets, Biclonics® and Triclonics® may be designed to provide a variety of mechanisms of action, including simultaneously blocking receptors that drive tumor cell growth and survival and mobilizing the patient's immune response by engaging T cells, and/or activating various killer cells to eradicate tumors.

Our technology platforms employ an assortment of patented technologies and techniques to generate human antibodies. We utilize our patented MeMo® mouse to produce a host of antibodies with diverse heavy chains and a common light chain that are capable of binding to virtually any antigen target. We use our patented heavy chain and CH3 domain dimerization technology to generate substantially pure bispecific and trispecific antibodies. We employ our patented Spleen to Screen® technology to efficiently screen panels of diverse heavy chains, designed to allow us to rapidly identify Biclonics® and Triclonics® therapeutic candidates with differentiated modes of action for pre-clinical and clinical testing.

Using our Biclonics® platform we have produced, and are currently developing, the following candidates: MCLA-128 (zenocutuzumab) for the potential treatment of solid tumors that harbor Neuregulin 1 (NRG1) gene fusions; MCLA-158 (petosemtamab) for the potential treatment of solid tumors; MCLA-145 for the potential treatment of solid tumors, and MCLA-129, for the potential treatment of lung and other solid tumors. Furthermore, we have a pipeline of proprietary antibody candidates in pre-clinical development and intend to further leverage our Biclonics® and Triclonics® technology platforms to identify multispecific antibody candidates and advance them into clinical development.

Funding Our Operations

We are a clinical-stage company and have not generated any revenue from product sales. We expect to incur significant expenses and operating losses for the foreseeable future as we advance our antibody candidates from discovery through pre-clinical development and into clinical trials and seek regulatory approval and pursue commercialization of any approved antibody candidate. In addition, if we obtain regulatory approval for any of our antibody candidates, if appropriate, we expect to incur significant commercialization expenses related to product manufacturing, marketing, sales and distribution.

We anticipate that we will require additional financing to support our continuing operations. Until such time as we can generate significant revenue from product sales, if ever, we expect to finance our operations through a combination of public or private equity or debt financings or other sources, which may include collaborations, business development and licensing opportunities with third parties. Adequate additional financing may not be available to us on acceptable terms, or at all. For example, the trading prices for our and other biopharmaceutical companies' stock have been highly volatile as a result of the COVID-19 pandemic. As a result, we may face difficulties raising capital through sales of our common stock and any such sales may be on unfavorable terms. See "Impact of



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COVID-19 Pandemic" below and "Risk Factors-Risks Related to Our Business and Industry-The COVID-19 pandemic caused by the novel coronavirus has and may continue to adversely impact our business, including our pre-clinical studies and clinical trials, financial condition and results of operations" in Part II, Item 1A of this Quarterly Report on Form 10-Q. Our inability to raise capital as and when needed would have a negative impact on our financial condition and our ability to pursue our business strategy. We will need to generate significant revenue to achieve profitability, and we may never do so.

Based on our current operating plan, we expect that our existing cash, cash equivalents and marketable securities of $396.8 million as of June 30, 2022 will be sufficient to fund our operations beyond 2024.

Clinical Programs

Zenocutuzumab, or "Zeno" (MCLA-128: HER3 x HER2 Biclonics®): NRG1 gene fusion (NRG1+) cancers and other solid tumors

We continue to enroll patients in the phase 1/2 eNRGy trial to assess the safety and anti-tumor activity of Zeno monotherapy in NRG1+ cancers.

In June 2022, we shared updated interim clinical data on our Zeno program (eNRGy trial and Early Access Program) in patients with NRG1 fusion (NRG1+) cancer at the American Society of Clinical Oncology (ASCO) 2022 Annual Meeting. Highlights from the presentation included:

As of the April 12, 2022 data cutoff date, 110 patients with NRG1+ cancer were treated with Zeno, and efficacy was assessed in 79 patients with measurable disease having the opportunity for 6 months or more follow-up and who met the criteria for the primary analysis population evaluable for response

Overall Response Rate (ORR) per RECIST criteria as assessed by investigator was 34% (27/79) (95% Cl: 24%-46%) across multiple tumor types

Pancreatic ductal adenocarcinoma ORR 42% (8/19) (95% CI: 20-67%)

Non-small cell lung cancer (NSCLC) ORR 35% (16/46) (95% CI: 21-50%)

Tumor shrinkage was observed in 70% of patients (55/79)

Median time to response was 1.8 months, and median duration of exposure was 6.3 months

Median duration of response was 9.1 months, and 20/83 patients were continuing treatment as of the data cutoff date

Zeno has demonstrated a consistent and well tolerated safety profile, with few grade 3 or 4 treatment-related adverse events

As announced in 2021, based on feedback received from the U.S. Food and Drug Administration, we believe that the eNRGy trial design and planned enrollment has the potential to support a Biologics License Application submission for Zeno for a tumor agnostic indication for the treatment of patients with NRG1+ cancer. To date, we have enrolled a cohort of patients that we believe may constitute a registrational data set, and continue to enroll patients to gather further safety and efficacy data on Zeno in NRG1+ cancer. We believe Zeno has the potential to be a first and best in class and a new standard of care for patients with NRG1+ cancer.

We believe the favorable safety profile of Zeno may also allow for future use and, potential benefit in combination with other cancer therapies. Accordingly, we are initiating a clinical trial evaluating Zeno in combination with afatinib for NRG1+ NSCLC. In addition, beyond NRG1+ cancer, we are initiating a clinical trial evaluating Zeno as a treatment for castration resistant prostate cancer, and are actively exploring the ways in which targeting both HER2 and HER3 with Zeno has potential for the treatment of other cancers.



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In August 2020, Zeno was granted Orphan Drug Designation by the U.S. FDA for the treatment of pancreatic cancer and in January 2021, we announced that Zeno received Fast Track Designation for the treatment of patients with metastatic solid tumors harboring NRG1 gene fusions that have progressed on standard-of-care therapy.

Petosemtamab, or "Peto" (MCLA-158: Lgr5 x EGFR Biclonics®): Solid Tumors Dose expansion continues in phase 1 trial: clinical update planned for 1H2023

We are developing petosemtamab for the potential treatment of solid tumors. Our phase 1 clinical trial of petosemtamab is ongoing in the dose expansion phase.

We plan to provide a clinical update for Peto at a medical conference in the first half of 2023. The planned presentation will provide the opportunity to present a robust update across the program, including approximately 40 patients with head and neck squamous cell carcinoma cohort with meaningful clinical follow up, and an update on the gastro-esophageal cohort, to inform clinical develop strategy and planned regulatory interactions.

MCLA-145 (CD137 x PD-L1 Biclonics®): Solid Tumors Phase 1 trial continues

We are developing MCLA-145 in an ongoing phase 1 trial for the potential treatment of solid tumors. MCLA-145 is designed to recruit, activate and prevent the exhaustion of tumor-infiltrating T-cells. The trial consists of a dose escalation phase, followed by a planned dose expansion phase. We are also planning to evaluate the combination of MCLA-145 with a PD-1 blocking antibody.



MCLA-129 (EGFR x c-MET Biclonics®): Solid Tumors
Phase 1 trial continues: clinical update planned for 2H2022

We are developing MCLA-129 as a potential treatment for solid tumors, including non-small cell lung cancer (NSCLC). In May 2021, we announced that the first patient was treated in the phase 1/2 dose escalation and expansion trial evaluating MCLA-129 for the treatment of patients with advanced NSCLC and other solid tumors. MCLA-129 is the subject to a collaboration and license agreement between us and Betta Pharmaceuticals Co. Ltd. (Betta), whereby we exclusively licensed Betta to develop MCLA-129 in China, while we retain full ex-China rights. In January 2021, Betta announced that the Chinese National Medical Products Administration had accepted its Investigational New Drug Application (IND) for MCLA-129 injection and in October 2021, Betta announced that the first patient was dosed in Betta's sponsored phase 1/2 trial of MCLA-129 in China in patients with advanced solid tumors.

In July 2022, we entered into a clinical supply agreement with AstraZeneca (LSE/STO/Nasdaq: AZN) for Tagrisso (osimertinib), a third-generation EGFR-TKI, for a planned investigation of the combination of Tagrisso and MCLA-129 in patients with non-small cell lung cancer in the dose expansion phase of the trial. Under the terms of the non-exclusive agreement, AstraZeneca will supply Tagrisso for use by us in the combination study.

We plan to provide a clinical update in the second half of 2022.

Impact of COVID-19 Pandemic

The current COVID-19 pandemic has presented a substantial public health and economic challenge around the world and is affecting our employees, communities, clinical trial sites and business operations, as well as the U.S. and Dutch economies and international financial markets.

While we are currently continuing our ongoing clinical trials, the COVID-19 pandemic and related precautions have directly or indirectly impacted enrollment, new, planned clinical trial site openings, patient visits, and on-site monitoring of our clinical trials and source verification of clinical data required for presentation of clinical data for zenocutuzumab, petosemtamab, MCLA-145 and MCLA-129. We have observed a low to moderate impact on clinical trial enrollment and operations, and a moderate impact on patient monitoring visits as a consequence of the COVID-19 pandemic during the second quarter ended June 30, 2022, with adjustments made to allow remote visits for some patient follow-up, and reduced onsite monitoring by the sponsor or contract research organization (CRO). We may further experience shortages of reagents or supplies necessary for certain clinical trial activities as a result of disruptions caused by COVID-19 associated supply chain issues. As a result of the COVID-19 pandemic, we may experience further disruptions that could severely impact our business, preclinical studies and clinical trials. The extent of the impact to our overall clinical development timeline is uncertain at this time and we continue to monitor and assess the COVID-19 pandemic on a regular basis.



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As a result of the COVID-19 pandemic, certain of our CROs and third-party suppliers, as well as collaborators in the U.S. and China that are developing or collaborating with us to develop certain of our pre-clinical and clinical-stage antibody candidates have been affected. As a result of such impact, we may face difficulties with and delays in performance of certain chemistry, manufacturing and controls and testing associated with our clinical candidates, including as it relates to sourcing materials required for such manufacture that may be diverted for other purposes associated with COVID-19, or difficulties or delays associated with testing of our pre-clinical antibody candidates associated with our collaborations with Incyte and Eli Lilly, which may delay or prevent their potential clinical development. While we currently do not anticipate any interruptions in our clinical trial supply of drug candidates, it is possible that the COVID-19 pandemic and response efforts may have an impact in the future on our third-party suppliers and contract manufacturing partners' ability to manufacture our clinical trial supply or source materials necessary for their manufacture.

In response to the spread of COVID-19, on March 18, 2020, we temporarily suspended our laboratory research activities at our facilities in Utrecht, the Netherlands to help secure the safety of our employees and to adhere to government recommendations of social distancing and limited public exposure in connection with the COVID-19 pandemic. We have since re-opened our offices and laboratory in Utrecht, and periodically employ social distancing and impose other requirements consistent with current government guidance. Further, we require that our employees in the U.S. and Netherlands follow requirements consistent with the guidance provided by the Center for Disease Control and Prevention (CDC), federal, state and local regulations for the U.S. and Dutch National Institute for Health and Environment or Het Rijksinstituut voor Volksgezondheid en Milieu (RIVM) for the Netherlands. While we use reasonable business practices to mitigate the risk of exposure to COVID-19 while on Company-operated premises, we cannot guarantee that traveling to and from and visiting the offices will not expose employees to infectious agents or eliminate inherent risks to our workforce and our business operations resulting from COVID-19. Given the uncertainty caused by the COVID-19 pandemic we cannot be certain that we will not suspend our laboratory research activities at our facilities or suspend use of our offices in the future.

At this time, there remains significant uncertainty caused by the COVID-19 pandemic and impact of related responses. The future impact of COVID-19 on our business and clinical trials will largely depend on future developments, which are highly uncertain and cannot be predicted with confidence. See "Risk Factors-Risks Related to Our Business and Industry-The COVID-19 pandemic caused by the novel coronavirus has and may continue to adversely impact our business, including our pre-clinical studies and clinical trials, financial condition and results of operations." in Part II, Item 1A of this Quarterly Report on Form 10-Q.

Collaborations

Refer to Item 1, "Business-Our Collaborations" and Note 12, "Collaborations," of the notes to our consolidated financial statements included in our Annual Report on Form 10-K and Note 8, "Collaborations," to our unaudited condensed consolidated interim financial statements elsewhere in this Quarterly Report on Form 10-Q for a description of the key terms of our arrangements.

Discussion and Analysis of our Results of Operations

Comparison of the three and six months ended June 30, 2022 and 2021

Revenue

The following is a comparison of revenue:



                     Three Months Ended                 Six Months Ended
                          June 30,                          June 30,
                 2022       2021      Change       2022       2021      Change
                        (In millions)                     (In millions)
Incyte          $  7.5     $  7.3     $   0.2     $ 13.8     $ 14.0     $  (0.2 )
Lilly              5.2        4.6         0.6       10.2        6.0         4.2
Other                -        0.5        (0.5 )      0.3        0.7        (0.4 )
Total revenue   $ 12.7     $ 12.4     $   0.3     $ 24.3     $ 20.7     $   3.6




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Collaboration revenue for the three months ended June 30, 2022 increased by $0.3 million as compared to the three months ended June 30, 2021, primarily as a result of an increase from Incyte revenue recognized and Lilly upfront payment amortization and reimbursement revenues of $0.2 million and $0.6 million respectively, partially offset by a decrease from Other upfront payment amortization and reimbursement revenues of $0.5 million. The Incyte increase is primarily driven by the achievement and recognition of a $1.0 million development milestone, offset by decreases in cost reimbursements of $0.2 million and amortization of upfront payments of $0.6 million. The change in exchange rates did not significantly impact collaboration revenue.

Collaboration revenue for the six months ended June 30, 2022 increased by $3.6 million as compared to the six months ended June 30, 2021, primarily as a result of an increase from Lilly upfront payment amortization and reimbursement revenues of $4.2 million partially offset by a decrease of Incyte revenue recognized of $0.2 million and a decrease in Other upfront payment amortization and reimbursement revenues of $0.4 million. The Incyte decrease is primarily driven by a decrease in amortization of upfront payments of $0.9 million and a decrease in cost reimbursements of $0.3 million, offset by the achievement and recognition of a $1.0 million development milestone in June 2022. The change in exchange rates did not significantly impact collaboration revenue.

As of June 30, 2022, we had total deferred revenue of $76.3 million, which primarily relates to the upfront payment received under our Incyte collaboration agreement and Lilly collaboration agreement and is expected to be recognized over the next four and two years, respectively.

Operating Expenses

The following is a comparison of operating expenses:



                                   Three Months Ended                 Six Months Ended
                                        June 30,                          June 30,
                              2022       2021       Change       2022       2021      Change
                                     (In millions)                      (In millions)
Research and development     $ 31.1     $ 24.6     $    6.5     $ 58.1     $ 45.4     $  12.7
General and administrative     12.7       10.6          2.1       24.4       19.9         4.5
Total operating expenses     $ 43.8     $ 35.2     $    8.6     $ 82.5     $ 65.3     $  17.2

Research and development expense for the three months ended June 30, 2022 increased by $6.5 million as compared to the three months ended June 30, 2021, primarily as a result of an increase personnel related expenses including stock-based compensation of $2.9 million due to an increase in employee headcount and an increase in external clinical services and drug manufacturing costs, including costs to fulfill our obligations under our collaboration agreements, related to our programs of $1.4 million.

Research and development expense for the six months ended June 30, 2022 increased by $12.7 million as compared to the six months ended June 30, 2021, primarily as a result of an increase in external clinical services and drug manufacturing costs, including costs to fulfill our obligations under our collaboration agreements, related to our programs of $5.2 million and an increase personnel related expenses including stock-based compensation of $5.0 million due to an increase in employee headcount.

General and administrative expense for the three months ended June 30, 2022 increased by $2.1 million as compared to the three months ended June 30, 2021, primarily as a result of an increase in stock-based compensation expense of $1.1 million, consulting costs of $0.7 million and personnel related expenses of $0.5 million due to an increase in employee headcount.

General and administrative expense for the six months ended June 30, 2022 increased by $4.5 million as compared to the six months ended June 30, 2021, primarily as a result of an increase in stock-based compensation expense of $2.2 million, personnel related expenses of $1.1 million due to an increase in employee headcount, and finance and human resources costs of $0.9 million.

Other Income (Loss), Net

The following is a comparison of other income, net:



                                      Three Months Ended                 Six Months Ended
                                           June 30,                          June 30,
                                  2022       2021      Change       2022       2021      Change
                                         (In millions)                     (In millions)

Interest (expense) income, net $ 0.3 $ (0.1 ) $ 0.4 $ 0.4 $ (0.1 ) $ 0.5 Foreign exchange gains

             24.6       (4.5 )      29.1       32.3        7.7        24.6

Other (losses) gains , net 0.6 0.1 0.5 1.1 (0.4 ) 1.5 Total other income (loss), net $ 25.5 $ (4.5 ) $ 30.0 $ 33.8 $ 7.2 $ 26.6






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Other income (loss), net consists of interest earned on our cash and cash equivalents held on account, accretion of investment earnings and net foreign exchange gains on our foreign denominated cash, cash equivalents and marketable securities. Other gains or losses relate to the issuance and settlement of financial instruments.

Income Tax Expense

The following is a comparison of income tax expense:


                                        Three Months Ended                 Six Months Ended
                                             June 30,                          June 30,
                                    2022       2021      Change      2022       2021      Change
                                           (In millions)                    (In millions)
Current                            $  0.3     $  0.2     $   0.1     $ 0.1     $ (0.2 )   $   0.3
Deferred                             (0.2 )     (0.1 )      (0.1 )     0.2        0.3        (0.1 )

Total tax expense (benefit), net $ 0.1 $ 0.1 $ - $ 0.3 $ 0.1 $ 0.2

We are subject to income taxes in the Netherlands and the U.S. Our current and deferred tax provision represents taxable income attributed to our U.S. operations as a consequence of allocating income to that jurisdiction. No current or deferred provision for income taxes has been made for income taxes in the Netherlands due to losses for tax purposes. Further, given a history of losses in the Netherlands, no deferred tax assets in excess of deferred tax liabilities are recognized as it is not more likely than not that they will be recovered.

Net Loss

Net loss for the three and six months ended June 30, 2022 was $5.7 million and $24.6 million respectively, compared to net loss for the three and six months ended June 30, 2021 of $27.4 million and $37.5 million respectively. The change in net loss was primarily due to the change in collaboration revenue, changes in operating expenses and changes in other income, net, as discussed above.

Material Changes in Financial Condition

Sources of Cash

As of June 30, 2022, we had $396.8 million in cash, cash equivalents and marketable securities that are available to fund our current operations. In addition to our existing cash, cash equivalents and marketable securities, we may receive research and development co-funding and are eligible to earn a significant amount of milestone payments under our collaboration agreements and research license agreements. Our ability to earn these payments and the timing of earning these payments is dependent upon the outcome of our research and development activities, and those of our collaborators and licensees, and is uncertain at this time.

As of June 30, 2022, the Company, pursuant to the Sales Agreement, had issued and sold an aggregate of 2,298,906 shares of its common stock resulting in gross proceeds of $49.5 million, before deducting sales agent commissions of $1.4 million.

Funding Requirements

Our primary uses of capital are clinical trial costs, chemistry, manufacturing and control costs to manufacture and supply drug product for our clinical trials, third-party research and development services, laboratory and related supplies, financial services, legal and other regulatory expenses and general overhead costs.

Because our product candidates are in various stages of clinical and pre-clinical development and the outcome of these efforts is uncertain, we cannot estimate the actual amounts necessary to successfully complete the development and commercialization of our product candidates or whether, or when, we may achieve profitability. In addition, the magnitude and duration of the COVID-19 pandemic and its impact on our liquidity and future funding requirements is uncertain as of the filing date of this Quarterly Report on Form 10-Q, as the pandemic continues to evolve globally. See "Impact of COVID-19 Pandemic" above and "Risk Factors-Risks Related to Our Business and Industry-The COVID-19 pandemic caused by the novel coronavirus has and may continue to adversely impact our business, including our pre-clinical studies and clinical trials, financial condition and results of operations" in Part II, Item 1A of this Quarterly Report on Form 10-Q for a further discussion of the possible impact of the COVID-19 pandemic on our business.

Until such time, if ever, as we can generate substantial product revenues, we expect to finance our cash needs through a combination of equity or debt financings, collaboration arrangements, license agreements, other business development opportunities with third parties and government grants.

Except for any obligations of our collaborators or licensees to make license, milestone or royalty payments under our agreements with them, and government grants, we do not have any committed external sources of liquidity and currently have no credit facility. To the extent that we raise additional capital through the future sale of equity or debt, the ownership interest of our stockholders may be diluted, and the terms of these securities may include liquidation or other preferences that adversely affect the rights of our existing common stockholders. Debt financing and preferred equity financing, if available, may involve agreements that include covenants



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limiting or restricting our ability to take specific actions, such as incurring additional debt, making capital expenditures or declaring dividends. If we raise additional funds through collaboration arrangements, license agreements or other business development opportunities in the future, we may have to relinquish valuable rights to our technologies or intellectual property, future revenue streams or product candidates or grant licenses on terms that may not be favorable to us. If we are unable to raise any additional funds that may be needed through equity or debt financings when needed, we may be required to delay, limit, reduce or terminate our product development or future commercialization efforts or grant rights to develop and market product candidates that we would otherwise prefer to develop and market ourselves.

Outlook

Based on our current operating plan, research and development plans and our timing expectations related to the progress of our programs, and the additional capital raised through the sale of equity during the quarter ended June 30, 2022, we expect that our existing cash, cash equivalents and marketable securities as of June 30, 2022 will be sufficient to fund our planned operating expenses and capital expenditure requirements beyond 2024. We have based this estimate on assumptions that may prove to be wrong, particularly as the process of testing product candidates in clinical trials is costly and the timing of progress in these trials is uncertain. As a result, we could use our capital resources sooner than we expect.

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