Merus 424B5 Prospectus supplement for primary offering

Filed Pursuant to Rule 424(b)(5)
Registration No. 333-233367

The information in this prospectus supplement is not complete and may be changed. We may not sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This prospectus supplement is not an offer to sell these securities, and we are not soliciting an offer to buy these securities in any state where the offer or sale is not permitted.

Subject to completion, dated November 4, 2019

PROSPECTUS SUPPLEMENT

$60,000,000

LOGO

Merus N.V.

Common Shares

We are selling $60.0 million of common shares.

We have granted the underwriters an option to purchase up to $9.0 million of additional shares.

Our common shares are listed on The Nasdaq Global Market under the symbol “MRUS.” The last reported sale price of our common shares on The Nasdaq Global Market on November 1, 2019 was $15.99 per share.

Investing in our common shares involves risks. See “Risk Factors” beginning on page 7.

We are an “emerging growth company” as defined by the Jumpstart Our Business Startups Act of 2012 and, as such, we have elected to comply with certain reduced public company reporting requirements for this prospectus supplement, the accompanying prospectus and future filings.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.


	Per Share	Total
Public Offering Price	$	$
Underwriting Discount(1)	$	$
Proceeds to Merus N.V. (before expenses)	$	$

(1)	We have agreed to reimburse the underwriters for certain expenses. See “Underwriting.”

The underwriters expect to deliver the common shares to purchasers on or about , 2019 through the book-entry facilities of The Depository Trust Company

Joint Book-Running Managers



Citigroup		Jefferies

Co-Manager

Kempen

, 2019.

TABLE OF CONTENTS

Prospectus Supplement


	Page
About this Prospectus Supplement		S-1
Prospectus Supplement Summary		S-2
Risk Factors		S-7
Special Note Regarding Forward-Looking Statements		S-10
Use of Proceeds		S-12
Dividend Policy		S-13
Capitalization		S-14
Dilution		S-15
Description of Share Capital		S-16
Certain Material Tax Considerations for U.S. Holders		S-20
Underwriting		S-24
Expenses		S-30
Legal Matters		S-30
Experts		S-30
Where You Can Find More Information; Incorporation by Reference		S-31

Accompanying Prospectus



About This Prospectus			1
Presentation of Financial Information			1
About the Company			2
Risk Factors			3
Special Note Regarding Forward-Looking Statements			4
Capitalization and Indebtedness			6
Use of Proceeds			7
Description of Share Capital and Articles of Association			8
Descriptions of Warrants			29
Description of Units			31
Global Securities			32
Plan of Distribution			36
Exchange Controls			38
Material Changes			38
Expenses			38
Legal Matters			38
Experts			38
Enforcement of Civil Liabilities			39
Where You Can Find More Information; Incorporation by Reference			40
Material Contracts			41

ABOUT THIS PROSPECTUS SUPPLEMENT

This prospectus supplement is part of a registration statement that we have filed with the Securities and Exchange Commission, or SEC, utilizing a “shelf” registration process, and relates to the offering of our common shares. Before buying any of the common shares that we are offering, we urge you to carefully read this prospectus supplement, the accompanying prospectus and the information incorporated by reference herein and therein, as well as the additional information described under the heading “Where You Can Find More Information; Incorporation by Reference.” These documents contain important information that you should consider when making your investment decision.

We provide information to you about this offering of our common shares in two separate documents that are bound together: (1) this prospectus supplement, which describes the specific details regarding this offering; and (2) the accompanying prospectus, which provides general information, some of which may not apply to this offering. Generally, when we refer to this “prospectus,” we are referring to both documents combined. If information in this prospectus supplement is inconsistent with the accompanying prospectus, you should rely on this prospectus supplement. To the extent there is a conflict between the information contained in this prospectus supplement, on the one hand, and the information contained in any document incorporated by reference in this prospectus supplement, on the other hand, you should rely on the information in this prospectus supplement. If any statement in one of these documents is inconsistent with a statement in another document having a later date—for example, a document incorporated by reference in this prospectus supplement—the statement in the document having the later date modifies or supersedes the earlier statement.

You should rely only on the information contained in or incorporated by reference in this prospectus supplement, the accompanying prospectus and any free writing prospectus that we may authorize for use in connection with this offering. We have not, and the underwriters have not, authorized anyone to provide you with different information. If anyone provides you with different or inconsistent information, you should not rely on it. You should assume that the information appearing in this prospectus supplement, the accompanying prospectus, the documents incorporated by reference herein and therein and any free writing prospectus that we have authorized for use in connection with this offering, is accurate only as of the date of those respective documents. Our business, financial condition, results of operations and prospects may have changed since those dates. You should read this prospectus supplement, the accompanying prospectus, the documents incorporated by reference herein and therein and any free writing prospectus that we have authorized for use in connection with this offering, in their entirety before making an investment decision.

We are offering to sell, and seeking offers to buy, our common shares only in jurisdictions where offers and sales are permitted. The distribution of this prospectus supplement and the accompanying prospectus and the offering of the common shares in certain jurisdictions may be restricted by law. Persons outside the United States who come into possession of this prospectus supplement and the accompanying prospectus must inform themselves about, and observe any restrictions relating to, the offering of the common shares and the distribution of this prospectus supplement and the accompanying prospectus outside the United States. This prospectus supplement and the accompanying prospectus do not constitute, and may not be used in connection with, an offer to sell, or a solicitation of an offer to buy, any securities offered by this prospectus supplement and the accompanying prospectus by any person in any jurisdiction in which it is unlawful for such person to make such an offer or solicitation.

When we refer to “Merus,” “we,” “our,” “us” and the “Company” in this prospectus, we mean Merus N.V. and its consolidated subsidiary, unless otherwise specified. When we refer to “you,” we mean the holders of the applicable securities.

This prospectus supplement may include trademarks, tradenames and service marks that are the property of us or other organizations. Solely for convenience, trademarks and tradenames referred to in this prospectus supplement appear without the^® and^™ symbols, but those references are not intended to indicate, in any way, that we will not assert, to the fullest extent under applicable law, our rights or that the applicable owner will not assert its rights, to these trademarks and tradenames.

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PROSPECTUS SUPPLEMENT SUMMARY

This summary highlights selected information contained elsewhere in this prospectus and in the documents we incorporate by reference. This summary does not contain all of the information you should consider before making an investment decision. You should read this entire prospectus carefully, especially the risks discussed under “Risk Factors” beginning on pageS-7 of this prospectus supplement, along with our consolidated financial statements and notes to those consolidated financial statements and the other information incorporated by reference in this prospectus supplement.

Our Company

We are a clinical-stage immuno-oncology company developing innovative bispecific antibody therapeutics. Our pipeline of full-length human bispecific antibody candidates, which we refer to as Biclonics^®, are generated from our Biclonics^® technology platform, which is able to generate a diverse array of antibody-heavy chains against virtually any target, paired with a common light chain. Two heavy chains paired with a common light chain can be combined to produce novel bispecific antibodies that bind to a diverse array of targets and display differentiated biology. By binding to two different targets, Biclonics^® can provide a variety of mechanisms of action. We are developing the following clinical candidates,MCLA-128 for the treatment of HER2-expressing solid tumors and other solid tumors with a focus on a rare, subpopulation of certain solid tumors referred to as NRG1 fusions,MCLA-117 for the treatment of acute myeloid leukemia,MCLA-158 for the potential treatment of solid tumors andMCLA-145, which is being developed in collaboration with Incyte Corporation, or Incyte, for the potential treatment of solid tumors. We are also developing a late-stage preclinical candidate,MCLA-129 for the potential treatment of solid tumors, which is being developed in collaboration with Betta Pharmaceuticals Co. Ltd., or Betta. We also have a pipeline of proprietary antibody candidates in preclinical development.

Recent Developments

MCLA-128

On October 25, 2019, we and investigators at Memorial Sloan Kettering Cancer Center, or MSKCC, announced acceptance of a presentation entitled “Clinicalproof-of-concept forMCLA-128, a bispecific HER2/3 antibody therapy, in NRG1 fusion-positive cancers” that was presented atAACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics on October 27, 2019 in Boston, Massachusetts, or the triple meeting.

On October 27, 2019, investigators from MSKCC provided an oral presentation at the triple meeting also entitled “Clinicalproof-of-concept forMCLA-128, a bispecific HER2/3 antibody therapy, in NRG1 fusion-positive cancers”, reporting a summary and initial data concerning the treatment of three cancer patients harboring NRG1 fusions withMCLA-128 at 750 mg administered intravenously every other week. These patients’ NRG1gene fusions were identified usingRNA-based sequencing. Assessments from this Early Access Program, or EAP, were conducted locally at MSKCC. All three patients exhibited tumor shrinkage, symptomatic improvement and durability up to their most recent assessment. All three patients remain on treatment as of October 29, 2019. Two of the EAP patients have pancreatic ductal adenocarcinoma, or PDAC, with one exhibiting a 54% reduction in tumor diameter at a confirmatory 5 months scan (partial response, or PR, by RECIST v1.1), and the other exhibiting a 25% reduction in tumor diameter at a confirmatory 5 months scan (stable disease, or SD, by RECIST v1.1). Both patients remain on treatment for over 7 months as of October 29, 2019. In the first patient, Positron Emission Tomography, or PET, imaging showed no evidence of metabolically active tumor and a relevant serum biomarker showed improvement within the first four weeks. Also within weeks of the first dose, the patient’s symptoms, including fatigue and weight loss, improved. In the second patient, PET imaging showed no evidence of metabolically active tumor. The patient’s tumor-related abdominal pain also improved following treatment. A

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third EAP patient treated at MSKCC hasnon-small cell lung cancer, or NSCLC, and exhibited a 41% reduction in tumor diameter at a confirmatory scan (PR by RECIST v1.1) and improvement in brain metastases. Prior toMCLA-128 treatment the patient progressed on six lines of therapy, including the tyrosine kinase inhibitor afatinib. The patient remains on treatment for approximately 5 months as of October 29, 2019.

On October 27, 2019, we also provided an update regardingMCLA-128 safety and tolerability in the Phase 1/2 clinical trial as of January 2019, wherein 117 patients treated with single-agentMCLA-128 with dosing regimens ranging from weekly to once every three weeks, reported mostly mild to moderate adverse events, or AEs. The incidence of grade 3 and 4 AEs irrespective of causality was 37% and 3%, respectively, with the incidence of suspected drug-related grade 3 AEs of about 4%, and no grade 4 events. One patient experienced a grade 5 hypersensitivity reaction, which was previously reported in Alsina et al. ESMO. 2018 #664P. As of October 29, 2019, the safety results forMCLA-128 in patients with cancers harboring NRG1 fusions have been consistent with what has been previously reported in the overall patient population treated withMCLA-128.

We further provided an overall update on ourMCLA-128 EAP and Phase 1/2 trial amended in June 2019 to focus on patients with solid tumors harboring an NRG1 fusion (eNRGy). As of October 27, 2019, nine patients identified with cancers harboring NRG1 fusions (three PDAC patients and six NSCLC patients) had been enrolled and treated withMCLA-128 across the EAP and eNRGy trial. Of the nine patients treated, six had at least one evaluation and all patients had previously progressed through standard of care.

Two PDAC patients were treated under the EAP (single patient investigational new drug applications, or INDs) at MSKCC as noted above. A third EAP PDAC patient was enrolled under a single patient IND outside of MSKCC. The patient received two treatments withMCLA-128, at a four-weeknon-standard interval due to the severity of the patient’s illness, and wasnon-evaluable, passing away due to complications related to the underlying disease prior to a first tumor evaluation.

Of the six NSCLC patients, one patient was treated under the EAP as noted above. The other five patients were enrolled in theMCLA-128 eNRGy clinical trial. Of these, one patient had SD for greater than 7 months but discontinued the trial due to poor adherence to the treatment protocol (unrelated to any AE or lack of efficacy); two patients had progressive disease and are no longer on the trial; and two patients have only recently started treatment and have not yet been assessed for response.

On October 27, 2019, we also provided an update regarding ourMCLA-128 Phase 2 trial, noting following enrollment completion, we do not have plans to advance into a Phase 3 clinical trial in metastatic breast cancer or gastric cancer in the absence of a collaborator and intend instead to refocus efforts on theMCLA-128 eNRGy trial as well as our other clinical and late-stage preclinical pipeline programs.

In patients enrolled as of August 31, 2019, we conducted an unplanned interim efficacy analysis with a datacut-off of October 23, 2019. For this analysis, Disease Control Rate, or DCR, which is the proportion of patients at first scheduled assessment who have achieved complete response, or CR, PR and or SD as the best overall response to therapy, and Overall Response Rate or ORR, which is the proportion of patients who have a partial or complete response as the best overall response to therapy, were estimated in both cohorts, “HER2+” and “ER+/HER2^low”, in our Phase 2 combination trial in metastatic breast cancer. Patients in the metastatic breast cancer trial were not evaluated for NRG1 fusions. In the HER2+ cohort, 24 patients were treated withMCLA-128 and a combination of trastuzumab and vinorelbine, and the estimated DCR observed was 75%. The estimated ORR was 4% (confirmed) and 17% (unconfirmed) including 3 PRs and 1 CR. All patients were previously treated with trastuzumab, pertuzumab, and an anti-HER2 antibody drug conjugate. The median number of prior lines of anti-HER2 therapy in the metastatic setting was three and 71% of patients had visceral involvement. In the ER+ cohort, 40 patients were treated withMCLA-128 and continuation of endocrine therapy on which they progressed prior to study entry, and the estimated DCR observed was 40%. The ORR was 0%. All patients were

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previously treated with CDK4/6 inhibitors. The median number of prior lines of endocrine therapy in the metastatic setting was two and 85% of patients had visceral involvement.

Enrollment in the ER+ cohort is now closed, having reached the minimum target accrual of 40 patients. We plan to continue to enroll another approximately 10 patients in the HER2+ cohort to reach the target accrual. We expect to present mature results, including the primary endpoint of clinical benefit rate at 24 weeks for both cohorts in this trial at a medical conference in 2020.

NRG1 Fusions

The NRG1 gene encodes for neuregulin (also known as heregulin), the ligand for HER3. Fusions between NRG1 and partner genes are rare, genetic events occurring in patients with certain lung, pancreatic and other solid tumors, associated with activation of HER2/HER3 signaling and growth of cancer cells. Overall projections for NRG1 fusions occurrence are based on limited published information at present. Based on the current literature available, we estimate that NRG1 fusions occur at a rate of approximately 0.3%—3.0% in NSCLC, 0.5%—1.5% in PDAC, and less than 1% in all other tumor types.

In preclinical studies, the mechanism by which the NRG1 fusion protein stimulates tumor growth has been observed to be especially sensitive to inhibition by theMCLA-128 Dock & Block^® mechanism of binding (docking) to HER2 and blocking the interaction of HER3 with its ligand neuregulin or with the NRG1 fusion protein. In preclinical studies, we have observed thatMCLA-128 is capable of potent inhibition of neuregulin -driven HER2/HER3 heterodimer formation and tumor growth in models harboring NRG1 fusions.

MCLA-117

Dose escalation in our Phase 1 clinical trial forMCLA-117 for the treatment of acute myeloid leukemia is ongoing and preliminary anti-tumor activity has been observed. In July 2019, we amended theMCLA-117 protocol to allow for the exploration of higher doses. We initiated the Phase 1 trial at a low dose level based on the potent nature ofT-cell engagers. Due to this amendment and continued dose escalation, we plan to present initial data from this trial at a medical conference in the first half of 2020.

MCLA-158

Dose escalation in the Phase 1 clinical trial ofMCLA-158 in patients with solid tumors is ongoing. We expect emerging data for the Phase 1 trial, including safety and information around the recommended Phase 2 dose, at the end of 2019. We plan to provide further guidance on the program in 2020.

MCLA-145

In May 2019, we commenced a Phase 1 clinical trial evaluating safety, tolerability, and preliminary efficacy ofMCLA-145 for the treatment of patients with advanced solid tumors. The Phase 1, open-label, single-agent clinical trial ofMCLA-145 consists of dose escalation followed by dose expansion. The primary objectives of the Phase 1 trial are dose finding and evaluation of safety and tolerability in patients with advanced solid tumors. The Phase 1 trial will also examine potential preliminary antitumor activity and functional target engagement of single-agentMCLA-145.MCLA-145 is the first product candidateco-developed under our global research collaboration with Incyte.

MCLA-129

On October 25, 2019, we announced acceptance of a presentation entitled “Preclinical evaluation ofMCLA-129: a bispecific antibody targetingc-MET and EGFR” that was presented at the triple meeting on October 29, 2019.

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MCLA-129 is an ADCC-enhanced Biclonics^® that inhibits the EGFR andc-MET signaling pathways in solid tumors. Preclinical data has shown thatMCLA-129 reverses resistance to tyrosine kinase resistant NSCLC cell lines resulting in tumor growth inhibition in xenograft models of NSCLC.MCLA-129 is designed to have two complementary mechanisms of action: blocking growth and survival pathways to stop tumor expansion and recruitment and enhancement of immune effector cells to eliminate the tumor.

Corporate Information

Our principal executive offices are located at Yalelaan 62, 3584 CM Utrecht, the Netherlands. Our telephone number at this address is +31 85 016 2500.

Our website address iswww.merus.nl. The information contained on, or that can be accessed through, our website is not a part of, and shall not be incorporated by reference into, this prospectus supplement.

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THE OFFERING

Common Shares Offered by Us

$60,000,000.

Underwriters Option to Purchase Additional Common Shares

We have granted the underwriters an option to purchase up to additional common shares. This option is exercisable, in whole or in part, for a period of 30 days from the date of this prospectus supplement.

Common Shares Outstanding Following this Offering

common shares ( if the underwriters exercise their option to purchase additional common shares in full).

Use of Proceeds

We currently intend to use the net proceeds of this offering to advance the clinical development of our product candidates for preclinical research and technology development and for working capital and general corporate purposes. See “Use of Proceeds.”

Risk Factors

You should read the “Risk Factors” section beginning on pageS-7 of this prospectus supplement and the other information included in, or incorporated by reference into, this prospectus supplement for a discussion of certain factors you should carefully consider before deciding to invest in our common shares.

Nasdaq Global Market Symbol

“MRUS”.

The number of our common shares to be outstanding after this offering is based on 23,407,552 common shares outstanding as of September 30, 2019 and excludes:

•

3,373,165 common shares issuable upon the exercise of share options outstanding as of September 30, 2019, at a weighted average exercise price of € 13.35 per share;

•

64,807 common shares issuable upon the vesting of restricted share units outstanding as of September 30, 2019; and

•

717,579 common shares reserved for future issuance under our 2016 Incentive Award Plan, or the 2016 Plan, and common shares that may become available pursuant to provisions in the 2016 Plan that automatically increase the share reserve under the 2016 Plan.

Unless otherwise indicated, this prospectus supplement reflects and assumes the following:

•

no exercise of the outstanding options or vesting of the restricted share units described above; and

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no exercise by the underwriters of their option to purchase additional common shares.

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RISK FACTORS

Investment in any securities offered pursuant to this prospectus supplement and the accompanying prospectus involves risks. You should carefully consider the risk factors described below and in our filings with the SEC incorporated by reference in this prospectus supplement. The occurrence of any of these risks might cause you to lose all or part of your investment in the offered securities.

Risks Related to the Development and Clinical Testing of Our Bispecific Antibody Candidates

We depend on enrollment of patients in our clinical trials for our bispecific antibody candidates. If we are unable to enroll patients in our clinical trials, our research and development efforts and business, financial condition and results of operations could be materially adversely affected.

Successful and timely completion of clinical trials will require that we enroll a sufficient number of patient candidates. For theMCLA-128 Phase 2 clinical trial, we plan to enroll approximately 80 patients with metastatic breast cancer in the United States and Europe. In the Phase 1 clinical trial ofMCLA-117, we plan to enroll approximately 50 adult patients with AML. In the Phase 1 clinical trial ofMCLA-158, we plan to enroll approximately 120 adult patients with colorectal cancer and possibly other solid tumors. In the planned Phase 1 clinical trial ofMCLA-145, we plan to enroll approximately 118 adult patients with solid tumors. These trials and other trials we conduct may be subject to delays as a result of patient enrollment taking longer than anticipated or patient withdrawal. For example, our Phase 1/2 single-agent trial ofMCLA-128 in solid tumors is enrolling patients harboring neuregulin 1, or NRG1, gene fusions. Patient populations with solid tumors with NRG1 gene fusions are small, which could result in slow enrollment of clinical trial participants.

Our clinical trials will also compete with other clinical trials for antibody candidates that are in the same therapeutic areas as our bispecific antibody candidates, and this competition will reduce the number and types of patients available to us, because some patients who might have opted to enroll in our trials may instead opt to enroll in a trial being conducted by one of our competitors. Because the number of qualified clinical investigators and clinical trial sites is limited, we expect to conduct some of our clinical trials at the same clinical trial sites that some of our competitors use, which will reduce the number of patients who are available for our clinical trials at such clinical trial sites.

Patient enrollment depends on many factors, including the size and nature of the patient population, eligibility criteria for the trial, the proximity of patients to clinical sites, the design of the clinical protocol, the availability of competing clinical trials, the availability of new drugs approved for the indication the clinical trial is investigating, and clinicians’ and patients’ perceptions as to the potential advantages of the drug being studied in relation to other available therapies. These factors may make it difficult for us to enroll enough patients to complete our clinical trials in a timely and cost-effective manner. Delays in the completion of any clinical trial of our bispecific antibody candidates will increase our costs, slow down our bispecific antibody candidate development and approval process, delay or potentially jeopardize our ability to commence product sales and generate revenue and harm our reputation and ability to obtain financing. In addition, some of the factors that cause, or lead to, a delay in the commencement or completion of clinical trials may also ultimately lead to the denial of regulatory approval of our bispecific antibody candidates.

Risks Related to Our Common Shares

As of the end of our most recent second fiscal quarter, we did not meet the requirements for being a foreign private issuer and, as of January 1, 2020, we will be required to comply with the provisions of the Securities Exchange Act of 1934, as amended, or the Exchange Act, and the rules of The Nasdaq Global Market, or Nasdaq, applicable to U.S. domestic issuers, which will require us to incur significant expenses and expend time and resources.

As of the end of our most recent second fiscal quarter, we did not meet the requirements for being a foreign private issuer. As a result, as of January 1, 2020, we will be required to comply with all of the provisions

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applicable to a U.S. domestic issuer under the Exchange Act, including filing an annual report on Form10-K, quarterly periodic reports and current reports for certain events, complying with the sections of the Exchange Act regulating the solicitation of proxies, requiring insiders to file public reports of their share ownership and trading activities and insiders being liable for profit from trades made in a short period of time. We will also be required to comply with the rules of Nasdaq applicable to U.S. domestic issuers, including that our articles of association specify a quorum of no less thanone-third of our outstanding voting common shares for meetings of our common shareholders, the solicitation of proxies and the approval by our shareholders in connection with certain events such as the acquisition of stock or assets of another company, the establishment of or amendments to equity-based compensation plans for employees, a change of control and certain private placements. In addition, we will be required to report our financial results under U.S. Generally Accepted Accounting Principles, including our historical financial results, which have previously been prepared in accordance with International Financial Reporting Standards. We expect to incur significant legal, accounting, insurance and other expenses and to expend greater time and resources, as we prepare for compliance, and comply, with these requirements.

We may be classified as a passive foreign investment company, or PFIC, for U.S. federal income tax purposes, which could result in adverse U.S. federal income tax consequences to U.S. investors in the common shares.

Based on the current and anticipated value of our assets, including goodwill, and the current and anticipated composition of our income, assets and operations, we do not believe we will be a PFIC for U.S. federal income tax purposes for our current taxable year. Anon-U.S. company will be considered a PFIC for any taxable year if (i) at least 75% of its gross income is passive income (including interest income), or (ii) at least 50% of the value of its assets (based on an average of the quarterly values of the assets during a taxable year) is attributable to assets that produce or are held for the production of passive income. The value of our assets generally is determined by reference to the market price of our common shares, which may fluctuate considerably. In addition, the composition of our income and assets is affected by how, and how quickly, we spend the cash we raise, including the proceeds from this offering. It is possible the Internal Revenue Service could determine that we were a PFIC for our current taxable year. If we were to be treated as a PFIC for any taxable year during which a U.S. Holder (as defined in the section of this Prospectus Supplement entitled “Certain Material Tax Considerations For U.S. Holders”) holds a common share, certain adverse U.S. federal income tax consequences could apply to such U.S. Holder. See “Certain Material Tax Considerations For U.S. Holders.”

Risks Relating to this Offering

If you purchase common shares sold in this offering, you will experience immediate and substantial dilution in the net tangible book value of your common shares. In addition, we may issue additional equity or convertible debt securities in the future, which may result in additional dilution to you.

The price per common share being offered may be higher than the net tangible book value per common share of our outstanding common shares prior to this offering. The sale of common shares after deducting underwriting commissions and discounts and estimated offering expenses payable by us will result in new investors in this offering incurring immediate dilution of $ per common share. For a more detailed discussion of the foregoing, see the section entitled “Dilution” in this prospectus supplement. To the extent outstanding share options are exercised or restricted share units vest, there will be further dilution to new investors. In addition, to the extent we need to raise additional capital in the future and we issue additional common shares or securities convertible, or exchangeable for, our common shares, our then existing shareholders will experience dilution and the new securities may have rights senior to those of our common shares.

We have broad discretion in the use of the net proceeds from this offering and may not use them effectively.

Our management will have broad discretion in the application of the net proceeds from this offering, including for any of the purposes described in the section entitled “Use of Proceeds,” and you will not have the opportunity as part of your investment decision to assess whether the net proceeds are being used appropriately. Because of

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the number and variability of factors that will determine our use of the net proceeds from this offering, their ultimate use may vary substantially from their currently intended use. Our management might not apply our net proceeds in ways that ultimately increase the value of your investment. We expect to use the net proceeds from this offering to advance the clinical development of our product candidates and for working capital and general corporate purposes. The failure by our management to apply these funds effectively could harm our business. Pending their use, we plan to invest the net proceeds from this offering in short- and intermediate-term, interest-bearing obligations and certificates of deposit. These investments may not yield a favorable return to our shareholders. If we do not invest or apply the net proceeds from this offering in ways that enhance shareholder value, we may fail to achieve expected financial results, which could cause our common share price to decline.

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SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus supplement, the accompanying prospectus and the documents incorporated by reference herein and therein contain statements that constitute forward-looking statements. Many of the forward-looking statements contained in this prospectus, the accompanying prospectus and the documents incorporated by reference herein and therein can be identified by the use of forward-looking words such as “anticipate,” “believe,” “could,” “expect,” “should,” “plan,” “intend,” “estimate” and “potential,” among others.

Forward-looking statements appear in a number of places in this prospectus, the accompanying prospectus and the documents incorporated by reference herein and therein and include, but are not limited to, statements regarding our intent, belief or current expectations. Forward-looking statements are based on our management’s beliefs and assumptions and on information currently available to our management. Such statements are subject to risks and uncertainties, and actual results may differ materially from those expressed or implied in the forward-looking statements due to various important factors, including, but not limited to, those referenced under the section titled “Risk Factors” in this prospectus supplement. Forward-looking statements include, but are not limited to, statements about:

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our operations as a clinical-stage company with a limited operating history and a history of operating losses;

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uncertainty about the initiation, timing, progress and results of clinical trials of our bispecific antibody candidates, including regarding when results of such trials will be made public;

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our expectations related to payments and clinical development under our collaboration agreement with Incyte Corporation, or Incyte;

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our clinical development plans forMCLA-128,MCLA-117,MCLA-158,MCLA-145, and the preclinical candidateMCLA-129;

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research and/or development of preclinical programs beingco-developed with Incyte, Simcere Pharmaceutical Group, and Betta Pharmaceuticals Co. Ltd, and for other bispecific antibody candidates;

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the timing or likelihood of regulatory filings and approvals for any of our bispecific antibody candidates;

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our ability to establish sales, marketing and distribution capabilities for any of our bispecific antibody candidates for which we may obtain regulatory approval;

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our ability to establish and maintain manufacturing arrangements for our bispecific antibody candidates;

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the scope of protection we are able to establish and maintain for intellectual property rights covering our bispecific antibody candidates and related technology;

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our ability to defend against any claims by third parties that we are infringing upon their intellectual property rights;

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our estimates regarding expenses, future revenues, capital requirements and our need for additional financing;

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the rate and degree of market acceptance of our bispecific antibody candidates;

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the impact of government laws and regulations on our business;

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our competitive position; and

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other risk factors under “Risk Factors” in this prospectus supplement, the accompanying prospectus or the documents incorporated by reference herein and therein.

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Forward-looking statements speak only as of the date they are made, and we do not undertake any obligation to update them in light of new information or future developments or to release publicly any revisions to these statements in order to reflect later events or circumstances or to reflect the occurrence of unanticipated events.

You should read this prospectus, the accompanying prospectus, and the documents incorporated by reference herein and therein completely and with the understanding that our actual results may differ materially from what we expect as expressed or implied by our forward-looking statements. In light of the significant risks and uncertainties to which our forward-looking statements are subject, you should not place undue reliance on or regard these statements as a representation or warranty by us or any other person that we will achieve our objectives and plans in any specified timeframe, or at all. We discuss many of these risks in greater detail in the documents incorporated by reference into this prospectus supplement and the accompanying prospectus. For all forward-looking statements, we claim the protection of the safe harbor for forward-looking statements contained in the Private Securities Litigation Reform Act of 1995.

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USE OF PROCEEDS

We estimate that the net proceeds from this offering will be approximately $ million (or approximately $ million if the underwriters exercise their option to purchase additional shares in full), after deducting the underwriting discounts and commissions and estimated offering expenses payable by us.

We currently intend to use the net proceeds of this offering to advance the clinical development of our product candidates, for preclinical research and technology development and for working capital and general corporate purposes.

We believe that our cash, cash equivalents and investments, together with the net proceeds from this offering, will fund our operations . We have not determined the amounts we plan to spend in any of the areas identified above or the timing of these expenditures. As a result, our management will have broad discretion to allocate the net proceeds to us from this offering, and investors will be relying on the judgment of our management regarding the application of the proceeds from this offering. We reserve the right to change the use of these proceeds as a result of certain contingencies such as competitive developments, the results of our commercialization efforts, acquisition and investment opportunities and other factors. Pending use of the proceeds as described above, we intend to invest the net proceeds of this offering in short-term, interest-bearing, investment-grade securities or certificates of deposit.

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DIVIDEND POLICY

We have never paid or declared any cash dividends on our common shares, and we do not anticipate paying any cash dividends on our common shares in the foreseeable future. We intend to retain all available funds and any future earnings to fund the development and expansion of our business.

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CAPITALIZATION AND INDEBTEDNESS

The following table sets forth our cash and cash equivalents and capitalization as of June 30, 2019 derived from our unaudited financial statements incorporated by reference into this prospectus supplement on:

•

an actual basis; and

•

an as adjusted basis to give effect to the sale by us of common shares in this offering after deducting underwriting discounts and commissions and estimated offering expenses payable by us in connection with this offering and assuming no exercise of the option to purchase additional common shares by the underwriters.

You should read the financial data in the following table in conjunction with our unaudited condensed consolidated financial statements, audited consolidated financial statements and related notes incorporated by reference into this prospectus supplement.


	As of June 30, 2019
	Actual		As Adjusted
	(unaudited)
Cash and cash equivalents	€		€

Shareholders’ equity:
Issued capital:
Common shares		2,105
Share premium		264,878
Accumulated loss

Total equity (deficit)

Total capitalization	€		€

The table above excludes:

•

3,282,510 common shares issuable upon the exercise of share options outstanding as of June 30, 2019 at a weighted average exercise price of €13.27 per share;

•

76,972 common shares issuable upon the vesting of restricted share units outstanding as of June 30, 2019; and

•

810,334 common shares reserved for future issuance under our 2016 Incentive Award Plan, or the 2016 Plan, and common shares that may become available pursuant to provisions in the 2016 Plan that automatically increase the share reserve under the 2016 Plan.

For purposes of this section, translations from U.S. dollars to Euros were made at the noon buying rate of the Federal Reserve Bank of New York on October 25, 2019, which was $1.1081 to €1.00. These translations should not be considered representations that any such amounts have been, could have been or could be converted into U.S. dollars at that or any other exchange rate as of that or any other date.

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DILUTION

If you invest in our common shares, your interest will be diluted to the extent of the difference between the price per common share you pay in this offering and the net tangible book value per common share immediately after this offering. Our net tangible book value as of June 30, 2019 was approximately $77.8 million, or approximately $3.32 per common share. Net tangible book value per share is equal to our total tangible assets, which excludes right to use assets, less our total liabilities, which includes lease liability, divided by the total number of ordinary shares outstanding as of June 30, 2019.

After giving effect to the sale of common shares in this offering after deducting the underwriting discounts and commissions and estimated offering expenses payable by us, our as adjusted net tangible book value as of June 30, 2019 would have been $ , or $ per common share. This represents an immediate increase in net tangible book value of $ per common share to our existing holders and an immediate decrease in net tangible book value of $ per common share to new investors in this offering.

Dilution per common share to new investors is determined by subtractingas-adjusted net tangible book value per common share after giving effect to this offering from the public offering price per common share paid by new investors. The following table illustrates this dilution on a per common share basis.


Assumed public offering price per common share			$
Net tangible book value per common share as of June 30, 2019	$	3.32
Increase in net tangible book value per common share attributable to the offering

As adjusted net tangible book value per common share after giving effect to the offering

Dilution per common share to new investors participating in the offering			$

The number of our common shares to be outstanding immediately after this offering is based on 23,393,287 common shares outstanding as of June 30, 2019, and excludes:

•

3,282,510 common shares issuable upon the exercise of share options outstanding as of June 30, 2019 at a weighted average exercise price of €13.27 per share;

•

76,972 common shares issuable upon the vesting of restricted share units outstanding as of June 30, 2019; and

•

The foregoing table does not give effect to the exercise of any outstanding options or vesting of any unvested restricted share units. To the extent options are exercised or restricted share units vest, there may be further dilution to new investors.

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DESCRIPTION OF SHARE CAPITAL

Set forth below is a summary of certain information concerning our share capital. Because the following is only a summary, it does not contain all of the information that may be important to you.

Share Capital

Common Shares

As of June 30, 2019, our issued share capital was €2,105,395.83 comprised of 23,393,287 common shares, nominal value €0.09 per share. As of June 30, 2019, our authorized share capital was comprised of 45,000,000 common shares and 45,000,000 preferred shares.

Preferred Shares

On May 24, 2016, we entered into a call option agreement with an independent foundation (stichting) under Dutch law called Stichting Continuïteit Merus, or the Protective Foundation, which agreement was most recently amended on August 27, 2018, pursuant to which the Protective Foundation would be allowed to acquire a number of preferred shares, which number is equal to the lesser of the following numbers: (i) the total number of shares (of whichever class) of our issued capital held by third parties immediately prior to the issuance of such preferred shares less the number of preferred shares already held by the Protective Foundation at that time (if any) and less one; or (ii) the maximum number of preferred shares that may be issued under our authorized capital as included in the Articles of Association, without approval by our general meeting of shareholders or our board of directors. As of June 30, 2019, there were no preferred shares outstanding, and we have no present plans to issue any preferred shares other than pursuant to an exercise by the Protective Foundation of its rights under the call option agreement.

History of Share Capital

Since January 1, 2016, our issued share capital has changed as provided below.

On March 16, 2016, we issued 12,107 common shares upon the exercise of options by the former Chairman of our board of directors (through the STAK) for aggregate consideration of €23,317 in cash.

On May 6, 2016, we effected a1-for-1.80 reverse share split of our common shares and all classes of our preferred shares issued at that time.

On May 19, 2016, in connection with the listing of our common shares on The Nasdaq Global Market, or Nasdaq, we effected a conversion of all issued and outstanding preferred shares into 8,627,712 common shares, and we issued a total of 1,312,718 common shares to holders of our preferred shares in satisfaction of accrued and unpaid dividends.

On May 24, 2016, we issued 5,500,000 common shares upon the closing of the initial public offering of our common shares, or IPO, at a price per share of $10.00. On May 26, 2016, we issued 639,926 common shares upon the exercise in part of the underwriters’ option to purchase additional shares. We received aggregate net proceeds of $53.3 million, after deducting underwriting discounts and commissions and offering expenses payable by us, from our IPO and the exercise of the underwriters’ option to purchase additional shares.

On January 23, 2017, we issued 3,200,000 common shares to Incyte Corporation at price per share of $25.00, for an aggregate purchase price of $80.0 million.

In January 2017, we issued 96,816 common shares upon the exercise of options by directors, officers, and employees for aggregate consideration of €189,574 in cash and granted 214,096 restricted share units, or RSUs.

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In February 2017, we issued 8,846 common shares upon the exercise of options by directors, officers, and employees for aggregate consideration of €18,865 in cash.

In May 2017, we issued 783 common shares upon the exercise of options by employees for aggregate consideration of €1,511 in cash.

In June 2017, we issued 4,424 common shares upon the exercise of options by employees for aggregate consideration of €16,858 in cash.

In July 2017, we issued 7,331 common shares upon the vesting of RSUs.

In September 2017, we issued 5,556 common shares upon the exercise of options by an employee for aggregate consideration of €10,723 in cash.

In October 2017, we issued 20,241 common shares upon the exercise of options by an employee for aggregate consideration of €69,088 in cash.

In January 2018, we issued 6,876 common shares upon the exercise of options by employees for aggregate consideration of €13,271 in cash and we issued 48,639 common shares upon the vesting of RSUs.

In February 2018, we issued 27,165 common shares upon the exercise of options by employees for aggregate consideration of €52,428 in cash and we issued 4,055 common shares upon the vesting of RSUs.

On February 15, 2018, we issued 3,099,997 common shares to certain new and existing investors at price per share of $18.00, for an aggregate purchase price of $55.8 million.

In July 2018, we issued 47,279 common shares upon the exercise of options by employees for aggregate consideration of €583,111 in cash.

In August 2018, we issued 1,750 common shares upon the exercise of options by employees for aggregate consideration of €23,865 in cash.

In September 2018, we issued 40,564 common shares upon the exercise of options by employees for aggregate consideration of €97,598 in cash.

In October 2018, we issued 12,254 common shares upon the exercise of options by employees for aggregate consideration of €106,179 in cash.

In December 2018, we issued 600,000 common shares to Regeneron Pharmaceuticals Inc. at a price per share of $25.00, for an aggregate purchase price of $15.0 million, or €13.1 million.

From March 2018 through December 2018, we issued 4,055 common shares upon the vesting of RSUs each month.

In January 2019, we issued 7,134 common shares upon the exercise of options by officers and employees for aggregate consideration of €22,406 in cash and issued 4,055 common shares upon the vesting of RSUs.

In February 2019, we issued 1,379 common shares upon the exercise of options by employees for aggregate consideration of €2,661 in cash and issued 4,055 common shares upon the vesting of RSUs.

From March 2019 through May 2019, we issued 4,055 common shares upon the vesting of RSUs each month.

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In June 2019, we issued 1,467 common shares upon the exercise of options by employees for aggregate consideration of €2,831 in cash and issued 4,055 common shares upon the vesting of RSUs.

In July 2019, we issued 2,100 common shares upon the exercise of options by employees for aggregate consideration of €14,803 in cash and issued 4,055 common shares upon vesting of RSUs.

From August 2019 through September 2019, we issued 4,055 common shares upon vesting of RSUs each month

Options

We have established equity incentive plans pursuant to which we have issued options to purchase common shares and RSUs to employees and directors. As of June 30, 2019, there were options and RSUs outstanding for 3,359,482 common shares.

The table below summarizes our share options outstanding as of June 30, 2019 that we have granted to our directors and our employees pursuant to our equity incentive plans. Share options granted under the Merus B.V. 2010 Employee Option Plan have a term of eight years from grant date and share options granted under the Merus N.V. Incentive Award 2016 Plan, as amended, have a term of ten years from grant date.

Share Options Granted Under the

Merus B.V. 2010 Employee Option Plan


Grant Date	Number of Share Options		Exercise Price Per Share Option
July 1, 2009 (employee)		556	€	13.50
October 1, 2009 (employee)		444	€	13.50
June 4, 2010 (officers and employees)		75,600	€	1.93
August 17, 2010 (officer)		7,556	€	1.93
September 15, 2010 (director and employee)		3,223	€	1.93
May 1, 2011 (employee)		333	€	1.93
September 9, 2011 (director)		1,042	€	1.93
November 3, 2011 (employees)		1,399	€	1.93
November 4, 2011 (director)		2,778	€	1.93
September 4, 2012 (officers and employees)		29,050	€	1.93
October 18, 2012 (directors)		3,820	€	1.93
June 17, 2013 (employees)		10,493	€	1.93
June 17, 2014 (officers and employees)		34,008	€	1.93
July 17, 2014 (directors)		8,022	€	1.93
March 16, 2015 (officers and employees)		167,233	€	1.93
June 4, 2015 (directors)		36,944	€	5.94
August 21, 2015 (directors)		36,632	€	7.20
October 30, 2015 (officers and employees)		432,766	€	7.20
December 16, 2015 (officer)		98,085	€	7.20
March 21, 2016 (directors)		25,112	€	8.46

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Share Options Granted Under the

Merus N.V. 2016 Incentive Award Plan, as amended


Grant Date	Number of Share Options		Exercise Price Per Share Option
May 18, 2016 (directors)		68,000	€	8.87
October 29, 2016 (officer)		219,890	$	18.41
November 1, 2016 (officer)		183,241	$	16.80
January 1, 2017 (officers)		707,734	$	21.11
January 17, 2017 (employees)		74,450	$	24.00
February 15, 2017 (employee)		50,000	$	25.90
March 13, 2017 (employee)		20,000	$	29.29
March 27, 2017 (employee)		1,300	$	25.00
April 13, 2017 (employee)		7,000	$	19.38
May 24, 2017 (directors)		33,900	$	18.23
May 29, 2017 (employees)		31,700	$	19.17
July 1, 2017 (employee)		20,000	$	15.85
October 4, 2017 (employee)		14,149	$	20.80
November 9, 2017 (employees)		54,500	$	15.95
February 21, 2018 (employees and officers)		435,468	$	17.94
April 4, 2018 (officer)		14,000	$	18.25
June 25, 2018 (advisor)		5,040	$	20.30
June 28, 2018 (director)		12,500	$	21.13
July 4, 2018 (advisor)		5,040	$	24.48
July 20, 2018 (director)		29,898	$	23.30
August 1, 2018 (advisor)		10,080	$	22.30
August 19, 2018 (employees)		39,450	$	19.10
October 24, 2018 (employees)		55,000	$	14.01
November 5, 2018 (director)		7,669	$	14.83
November 16, 2018 (employee)		4,200	$	14.06
January 10, 2019 (director)		17,000	$	14.39
February 20, 2019 (officers and employees)		842,071	$	11.16
March 19, 2019 (director)		17,000	$	12.54
March 21, 2019 (employees)		5,600	$	12.89
April 23, 2019 (employees)		1,800	$	15.09
May 1, 2019 (employees)		26,400	$	15.67
May 28, 2019 (employee)		10,000	$	13.02
June 3, 2019 (employees)		11,800	$	13.74
June 6, 2019 (employees)		23,300	$	13.23
June 12, 2019 (directors)		51,000	$	13.35
June 24, 2019 (employees)		3,700	$	14.09

Restricted Share Units Granted Under the

Merus N.V. 2016 Incentive Award Plan, as amended


Grant Date	Number of Share Subject to Vesting
January 1, 2017 (officers)		214,096

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CERTAIN MATERIAL TAX CONSIDERATIONS FOR U.S. HOLDERS

The following is a description of certain material U.S. federal income tax consequences to the U.S. Holders described below of owning and disposing of our common shares. It is not a comprehensive description of all tax considerations that may be relevant to a particular person’s decision to acquire our common shares. This discussion applies only to a U.S. Holder that holds our common shares as a capital asset for tax purposes (generally, property held for investment). In addition, it does not describe all of the tax consequences that may be relevant in light of a U.S. Holder’s particular circumstances, including state and local tax consequences, estate tax consequences, alternative minimum tax consequences, the potential application of the provisions of the United States Internal Revenue Code of 1986, as amended, or the Code, known as the Medicare contribution tax on net investment income, or any item of gross income with respect to our common stock being taken into account in an “applicable financial statement” (as defined in the Code), and tax consequences applicable to U.S. Holders subject to special rules, such as:

•

certain financial institutions;

•

dealers or traders in securities who use amark-to-market method of tax accounting;

•

U.S. expatriates and certain former citizens or long-term residents of the United States;

•

persons holding our common shares as part of a hedging transaction, “straddle,” wash sale, conversion transaction or integrated transaction or persons entering into a constructive sale with respect to our common shares;

•

persons whose “functional currency” for U.S. federal income tax purposes is not the U.S. dollar;

•

tax exempt entities, including “individual retirement accounts” and “Roth IRAs”, or government organizations;

•

S corporations or entities classified as partnerships for U.S. federal income tax purposes;

•

regulated investment companies or real estate investment trusts;

•

persons who acquired our common shares pursuant to the exercise of an employee stock option or otherwise as compensation;

•

persons that own or are deemed to own ten percent or more of our shares by vote or value; and

•

persons holding our common shares in connection with a trade or business conducted outside the United States.

If an entity or arrangement that is classified as a partnership for U.S. federal income tax purposes holds our common shares, the U.S. federal income tax treatment of a partner will generally depend on the status of the partner and the activities of the partnership. Partnerships holding our common shares and partners in such partnerships are encouraged to consult their tax advisers as to the particular U.S. federal income tax consequences of holding and disposing of our common shares.

The discussion is based on the Code, administrative pronouncements, judicial decisions, final, temporary and proposed Treasury Regulations, and the income tax treaty between the Netherlands and the United States, or the Treaty, all as of the date hereof, changes to any of which may affect the tax consequences described herein—possibly with retroactive effect.

A “U.S. Holder” is a holder who, for U.S. federal income tax purposes, is a beneficial owner of our common shares who is eligible for the benefits of the Treaty and is:

(1)

a citizen or individual resident of the United States;

(2)

a corporation, or other entity taxable as a corporation, created or organized in or under the laws of the United States, any state therein or the District of Columbia;

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(3)

an estate, the income of which is subject to U.S. federal income taxation regardless of its source; or

(4)

a trust that (a) is subject to the primary supervision of a U.S. court and the control of one or more “United States persons” (within the meaning of Section 7701(a)(30) of the Code) or (b) has a valid election in effect to be treated as a United States person for U.S. federal income tax purposes.

U.S. Holders are encouraged to consult their tax advisers concerning the U.S. federal, state, local and foreign tax consequences of owning and disposing of our common shares in their particular circumstances.

Taxation of Distributions

Subject to the discussion below under “Passive Foreign Investment Company Rules,” distributions paid on our common shares, other than certain pro rata distributions of our common shares, will generally be treated as dividends to the extent paid out of our current or accumulated earnings and profits (as determined under U.S. federal income tax principles). Because we do not calculate our earnings and profits under U.S. federal income tax principles, we expect that distributions generally will be reported to U.S. Holders as dividends. Subject to applicable limitations, dividends paid to certainnon-corporate U.S. Holders may be taxable at preferential rates applicable to “qualified dividend income.” However, the qualified dividend income treatment may not apply if we are treated as a PFIC with respect to the U.S. Holder in the taxable year of the distribution or the preceding taxable year. The amount of a dividend will include any amounts withheld by us in respect of Dutch income taxes. The amount of the dividend will be treated as foreign-source dividend income to U.S. Holders and will not be eligible for the dividends-received deduction generally available to U.S. corporations under the Code. Dividends will be included in a U.S. Holder’s income on the date of the U.S. Holder’s receipt of the dividend. The amount of any dividend income paid in foreign currency will be the U.S. dollar amount calculated by reference to the exchange rate in effect on the date of actual or constructive receipt, regardless of whether the payment is in fact converted into U.S. dollars. If the dividend is converted into U.S. dollars on the date of receipt, a U.S. Holder should not be required to recognize foreign currency gain or loss in respect of the dividend income. A U.S. Holder may have foreign currency gain or loss if the dividend is converted into U.S. dollars after the date of receipt. Such gain or loss would generally be treated as U.S.-source ordinary income or loss. The amount of any distribution of property other than cash (and other than certain pro rata distributions of our common shares or rights to acquire our common shares) will be the fair market value of such property on the date of distribution.

Subject to applicable limitations, some of which vary depending upon the U.S. Holder’s particular circumstances, Dutch income taxes withheld from dividends on our common shares at a rate not exceeding the rate provided by the Treaty will be creditable against the U.S. Holder’s U.S. federal income tax liability. The rules governing foreign tax credits are complex and U.S. Holders should consult their tax advisers regarding the creditability of foreign taxes in their particular circumstances. In lieu of claiming a foreign tax credit, U.S. Holders may, at their election, deduct foreign taxes, including any Dutch income tax, in computing their taxable income, subject to generally applicable limitations under U.S. law. An election to deduct foreign taxes instead of claiming foreign tax credits applies to all foreign taxes paid or accrued in the taxable year.

Sale or Other Taxable Disposition of Our Common Shares

Subject to the discussion below under “Passive Foreign Investment Company Rules,” gain or loss realized on the sale or other taxable disposition of our common shares will be capital gain or loss, and will be long-term capital gain or loss if the U.S. Holder held our common shares for more than one year. The amount of the gain or loss will equal the difference between the U.S. Holder’s tax basis in the common shares disposed of and the amount realized on the disposition, in each case as determined in U.S. dollars. This gain or loss will generally be U.S.-source gain or loss for foreign tax credit purposes. The deductibility of capital losses is subject to limitations.

If the consideration received by a U.S. Holder is not paid in U.S. dollars, the amount realized will be the U.S. dollar value of the payment received determined by reference to the spot rate of exchange on the date of the

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sale or other disposition. However, if our common shares are treated as traded on an “established securities market” and the U.S. Holder is either a cash basis taxpayer or an accrual basis taxpayer that has made a special election (which must be applied consistently from year to year and cannot be changed without the consent of the United States Internal Revenue Service, or IRS), such holder will determine the U.S. dollar value of the amount realized in anon-U.S. dollar currency by translating the amount received at the spot rate of exchange on the settlement date of the sale. If a U.S. Holder is an accrual basis taxpayer that is not eligible to or does not elect to determine the amount realized using the spot rate on the settlement date, such holder will recognize foreign currency gain or loss to the extent of any difference between the U.S. dollar amount realized on the date of sale or disposition and the U.S. dollar value of the currency received at the spot rate on the settlement date.

Passive Foreign Investment Company Rules

•

at least 75% of its gross income is passive income; or

•

at least 50% of its gross assets (determined on the basis of a quarterly average) is attributable to assets that produce passive income or are held for the production of passive income.

We will be treated as owning our proportionate share of the assets and earning our proportionate share of the income of any other corporation in which we own, directly or indirectly, 25% or more (by value) of the equity.

A separate determination must be made after the close of each taxable year as to whether we are a PFIC for that year. As a result, our PFIC status may change. In particular, the total value of our assets for purposes of the asset test generally will be calculated using the market price of our common shares, which may fluctuate considerably. Fluctuations in the market price of our common shares may result in our being a PFIC for any taxable year. In addition, the composition of our income and assets is affected by how, and how quickly, we spend the cash we raise in any offering, including the proceeds from this offering.

If we are classified as a PFIC in any year with respect to which a U.S. Holder owns our common shares, we will continue to be treated as a PFIC with respect to such U.S. Holder in all succeeding years during which the U.S. Holder owns such common shares, regardless of whether we continue to meet the tests described above unless (1) we cease to be a PFIC and the U.S. Holder has made a “deemed sale” election under the PFIC rules, or (2) the U.S. Holder makes a QEF Election (defined below) with respect to taxable years in which we are a PFIC.

If we are a PFIC for any taxable year, U.S. Holders will be subject to special tax rules with respect to any “excess distribution” that they receive and any gain they realize from a sale or other disposition (including a pledge) of our common shares. Distributions U.S. Holders receive in a taxable year that are greater than 125% of the average annual distributions they received during the shorter of the three preceding taxable years or their holding period for our common shares will be treated as an excess distribution. Under these special tax rules:

•

the excess distribution or gain will be allocated ratably over their holding period for our common shares;

•

the amount allocated to the current taxable year, and any taxable year prior to the first taxable year in which we became a PFIC, will be treated as ordinary income; and

•

the amount allocated to each other year will be subject to the highest tax rate in effect for that year and the interest charge generally applicable to underpayments of tax will be imposed on the resulting tax attributable to each such year.

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The tax liability for amounts allocated to years prior to the year of disposition or “excess distribution” cannot be offset by any net operating losses for such years, and gains (but not losses) realized on the sale of our common shares cannot be treated as capital, even if U.S. Holders hold our common shares as capital assets.

Certain elections may be available that would result in alternative treatments. U.S. Holders can avoid the interest charge on excess distributions or gain relating to our common shares by making amark-to-market election with respect to our common shares, provided that our common shares are “marketable.” Our common shares will be marketable if they are “regularly traded” on certain U.S. stock exchanges or on a foreign stock exchange that meets certain conditions. The adverse consequences of owning stock in a PFIC could also be mitigated if a U.S. Holder makes a valid “qualified electing fund” election, or QEF election, which, among other things, would require a U.S. Holder to include currently in income itspro rata share of the PFIC’s net capital gain and ordinary earnings, based on earnings and profits as determined for U.S. federal income tax purposes.

Unless otherwise provided by the U.S. Treasury, each U.S. shareholder of a PFIC is required to file an annual report containing such information as the U.S. Treasury may require. A U.S. Holder’s failure to file the annual report will cause the statute of limitations for such U.S. Holder’s U.S. federal income tax return to remain open with regard to the items required to be included in such report until three years after the U.S. Holder files the annual report, and, unless such failure is due to reasonable cause and not willful neglect, the statute of limitations for the U.S. Holder’s entire U.S. federal income tax return will remain open during such period.

If we are or become a PFIC, U.S. Holders should consult their tax advisors regarding any reporting requirements that may apply to them. U.S. Holders are urged to consult their tax advisors regarding the application of the PFIC rules to the ownership and disposition of our common shares and the potential availability of amark-to-market or QEF election.

Information Reporting and Backup Withholding

Payments of dividends and sales proceeds that are made within the United States or through certain U.S.-related financial intermediaries generally are subject to information reporting, and may be subject to backup withholding, unless (i) the U.S. Holder is a corporation or other exempt recipient or (ii) in the case of backup withholding, the U.S. Holder provides a correct taxpayer identification number and certifies that it is not subject to backup withholding.

Backup withholding is not an additional tax. The amount of any backup withholding from a payment to a U.S. Holder will be allowed as a credit against the holder’s U.S. federal income tax liability and may entitle it to a refund, provided that the required information is timely furnished to the IRS.

Information with Respect to Foreign Financial Assets

Certain U.S. Holders who are individuals (and, under proposed regulations, certain entities) may be required to report information relating to our common shares, subject to certain exceptions (including an exception for our common shares held in accounts maintained by certain U.S. financial institutions). U.S. Holders should consult their tax advisers regarding their reporting obligations with respect to their ownership and disposition of our common shares.

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UNDERWRITING

Citigroup Global Markets Inc. and Jefferies LLC are acting as joint book-running managers of the offering and as representatives of the underwriters named below. Subject to the terms and conditions stated in the underwriting agreement dated the date of this prospectus supplement, each underwriter named below has severally agreed to purchase, and we have agreed to sell to that underwriter, the number of shares set forth opposite the underwriter’s name.


Underwriter		Number of Common Shares
Citigroup Global Markets Inc.
Jefferies LLC
Kempen & Co U.S.A., Inc.

Total

The underwriting agreement provides that the obligations of the underwriters to purchase the common shares included in this offering are subject to approval of legal matters by counsel and to other conditions. The underwriters are obligated to purchase all the common shares (other than those covered by the underwriters’ option to purchase additional shares described below) if they purchase any of the common shares.

Shares sold by the underwriters to the public will initially be offered at the initial public offering price set forth on the cover of this prospectus supplement. Any shares sold by the underwriters to securities dealers may be sold at a discount from the initial public offering price not to exceed $ per share. If all the common shares are not sold at the initial offering price, the underwriters may change the offering price and the other selling terms. Sales of the common shares made outside of the United States may be made by affiliates of the underwriters

If the underwriters sell more shares than the total number set forth in the table above, we have granted to the underwriters an option, exercisable for 30 days from the date of this prospectus supplement, to purchase up to $9.0 million of additional common shares at the public offering price less the underwriting discount. To the extent the option is exercised, each underwriter must purchase a number of additional shares approximately proportionate to that underwriter’s initial purchase commitment. Any shares issued or sold under the option will be issued and sold on the same terms and conditions as the other shares that are the subject of this offering.

We and our officers, directors and certain of our shareholders have agreed that, subject to specified limited exceptions, we and they will not for a period of 90 days from the date of this prospectus supplement, without the prior written consent of Citigroup Global Markets Inc. and Jefferies LLC, offer, sell, contract to sell, pledge or otherwise dispose of, (or enter into any transaction which is designed to, or might reasonably be expected to, result in the disposition of), directly or indirectly, or hedge any shares or any securities convertible into or exchangeable for our common shares. Citigroup Global Markets Inc. and Jefferies LLC in their sole discretion may release any of the securities subject tothese lock-up agreements at any time without notice.

The common shares are listed on the Nasdaq Global Market under the symbol “MRUS.”

The following table shows the underwriting discounts and commissions that we are to pay to the underwriters in connection with this offering. These amounts are shown assuming both no exercise and full exercise of the underwriters’ option to purchase additional shares.


	Paid by Merus N.V.
	No Exercise	Full Exercise
Per share	$	$
Total	$	$

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We estimate that our total expenses of this offering, excluding underwriting discounts and commissions, will be approximately $450,000. We have also agreed to reimburse the underwriters for certain expenses incurred by them in connection with this offering in an amount up to $30,000.

In connection with the offering, the underwriters may purchase and sell shares in the open market. Purchases and sales in the open market may include short sales, purchases to cover short positions, which may include purchases pursuant to the underwriters’ option to purchase additional shares and stabilizing purchases.

•

Short sales involve secondary market sales by the underwriters of a greater number of shares than they are required to purchase in the offering.

•

“Covered” short sales are sales of shares in an amount up to the number of shares represented by the underwriters’ option to purchase additional shares.

•

“Naked” short sales are sales of shares in an amount in excess of the number of shares represented by the underwriters’ option to purchase additional shares.

•

Covering transactions involve purchases of shares either pursuant to the underwriters’ option to purchase additional shares or in the open market in order to cover short positions.

•

To close a naked short position, the underwriters must purchase shares in the open market. A naked short position is more likely to be created if the underwriters are concerned that there may be downward pressure on the price of the common shares in the open market after pricing that could adversely affect investors who purchase in the offering.

•

To close a covered short position, the underwriters must purchase shares in the open market or must exercise the option to purchase additional shares. In determining the source of shares to close the covered short position, the underwriters will consider, among other things, the price of shares available for purchase in the open market as compared to the price at which they may purchase shares through the underwriters’ option to purchase additional shares.

•

Stabilizing transactions involve bids to purchase shares so long as the stabilizing bids do not exceed a specified maximum.

Purchases to cover short positions and stabilizing purchases, as well as other purchases by the underwriters for their own accounts, may have the effect of preventing or retarding a decline in the market price of the common shares. They may also cause the price of the common shares to be higher than the price that would otherwise exist in the open market in the absence of these transactions. The underwriters may conduct these transactions on the Nasdaq Global Market, inthe over-the-counter market or otherwise. If the underwriters commence any of these transactions, they may discontinue them at any time.

In addition, in connection with this offering, some of the underwriters (and selling group members) may engage in passive market making transactions in the common shares on the Nasdaq Global Market, prior to the pricing and completion of the offering. Passive market making consists of displaying bids on the Nasdaq Global Market no higher than the bid prices of independent market makers and making purchases at prices no higher than those independent bids and effected in response to order flow. Net purchases by a passive market maker on each day are limited to a specified percentage of the passive market maker’s average daily trading volume in the common shares during a specified period and must be discontinued when that limit is reached. Passive market making may cause the price of the common shares to be higher than the price that otherwise would exist in the open market in the absence of those transactions. If the underwriters commence passive market making transactions, they may discontinue them at any time.

Conflicts of Interest

The underwriters are full service financial institutions engaged in various activities, which may include securities trading, commercial and investment banking, financial advisory, investment management, principal

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investment, hedging, financing and brokerage activities. The underwriters and their respective affiliates have in the past performed commercial banking, investment banking and advisory services for us from time to time for which they have received customary fees and reimbursement of expenses and may, from time to time, engage in transactions with and perform services for us in the ordinary course of their business for which they may receive customary fees and reimbursement of expenses. In the ordinary course of their various business activities, the underwriters and their respective affiliates may make or hold a broad array of investments and actively trade debt and equity securities (or related derivative securities) and financial instruments (which may include bank loans and/or credit default swaps) for their own account and for the accounts of their customers and may at any time hold long and short positions in such securities and instruments. Such investments and securities activities may involve securities and/or instruments of ours or our affiliates. The underwriters and their affiliates may also make investment recommendations and/or publish or express independent research views in respect of such securities or financial instruments and may hold, or recommend to clients that they acquire, long and/or short positions in such securities and instruments.

We have agreed to indemnify the underwriters against certain liabilities, including liabilities under the Securities Act, or to contribute to payments the underwriters may be required to make because of any of those liabilities.

Notice to Prospective Investors in the European Economic Area

In relation to each member state of the European Economic Area or EEA Member State, no shares have been offered or will be offered pursuant to the offering to the public in that EAA Member State prior to the publication of a prospectus in relation to the shares which has been approved by the competent authority in that EAA Member State or, where appropriate, approved in another EAA Member State and notified to the competent authority in that EAA Member State, all in accordance with the Prospectus Regulation, except that an offer to the public in that EEA Member State of any of our shares may be made at any time under the following exemptions under the Prospectus Regulation:

•

to any legal entity which is a “qualified investor” as defined in the Prospectus Regulation;

•

to fewer than 150, natural or legal persons, other than qualified investors as defined in the Prospectus Regulation, as permitted under the Prospectus Regulation, subject to obtaining the prior consent of the underwriters or the underwriters nominated by us for any such offer; or

•

in any other circumstances falling within Article 1(4) of the Prospectus Regulation,

provided that no such offer of shares shall require us or any underwriter to publish a prospectus pursuant to Article 3 of the Prospectus Regulation or supplement a prospectus pursuant to Article 23 of the Prospectus Regulation.

For the purposes of this provision, the expression an “offer to the public” in relation to any offer of shares in any EEA Member State means the communication in any form and by any means of sufficient information on the terms of the offer and any shares to be offered so as to enable an investor to decide to purchase or subscribe for the shares and the expression “Prospectus Regulation” means Regulation (EU) 2017/1129.

The sellers of the shares have not authorized and do not authorize the making of any offer of shares through any financial intermediary on their behalf, other than offers made by the underwriters with a view to the final placement of the shares as contemplated in this prospectus supplement. Accordingly, no purchaser of the shares, other than the underwriters, is authorized to make any further offer of the shares on behalf of the sellers or the underwriters.

Notice to Prospective Investors in the United Kingdom

This prospectus supplement and the accompanying prospectus are only being distributed to, and is only directed at, persons in the United Kingdom that are qualified investors within the meaning of Article 2(1)(e) of

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the Prospectus Regulation that are also (i) investment professionals falling within Article 19(5) of the Financial Services and Markets Act 2000 (Financial Promotion) Order 2005 (the “Order”) or (ii) high net worth entities, and other persons to whom it may lawfully be communicated, falling within Article 49(2)(a) to (d) of the Order (each such person being referred to as a “relevant person”). This prospectus supplement and its contents are confidential and should not be distributed, published or reproduced (in whole or in part) or disclosed by recipients to any other persons in the United Kingdom. Any person in the United Kingdom that is not a relevant person should not act or rely on this document or any of its contents.

Notice to Prospective Investors in France

Neither this prospectus supplement nor any other offering material relating to the shares described in this prospectus supplement has been submitted to the clearance procedures of the Autorité des Marchés Financiers or of the competent authority of another member state of the European Economic Area and notified to the Autorité des Marchés Financiers. The shares have not been offered or sold and will not be offered or sold, directly or indirectly, to the public in France. Neither this prospectus supplement nor any other offering material relating to the shares has been or will be:

•

released, issued, distributed or caused to be released, issued or distributed to the public in France; or

•

used in connection with any offer for subscription or sale of the shares to the public in France.

Such offers, sales and distributions will be made in France only:

•

to qualified investors (investisseurs qualifiés) and/or to a restricted circle of investors (cercle restreint d’investisseurs), in each case investing for their own account, all as defined in, and in accordance witharticles L.411-2, D.411-1, D.411-2, D.734-1, D.744-1, D.754-1 and D.764-1 of the French Code monétaire et financier;

•

to investment services providers authorized to engage in portfolio management on behalf of third parties; or

•

in a transaction that, in accordance witharticle L.411-2-II-1°-or-2°-or 3° of the French Code monétaire et financier andarticle 211-2 of the General Regulations (Règlement Général) of the Autorité des Marchés Financiers, does not constitute a public offer (appel public à l’épargne).

The shares may be resold directly or indirectly, only in compliance with articlesL.411-1,L.411-2,L.412-1 andL.621-8 throughL.621-8-3 of the French Code monétaire et financier.

Notice to Prospective Investors in Hong Kong

The shares may not be offered or sold in Hong Kong by means of any document other than (i) in circumstances which do not constitute an offer to the public within the meaning of the Companies Ordinance (Cap. 32, Laws of Hong Kong), or (ii) to “professional investors” within the meaning of the Securities and Futures Ordinance (Cap. 571, Laws of Hong Kong) and any rules made thereunder, or (iii) in other circumstances which do not result in the document being a “prospectus” within the meaning of the Companies Ordinance (Cap. 32, Laws of Hong Kong) and no advertisement, invitation or document relating to the shares may be issued or may be in the possession of any person for the purpose of issue (in each case whether in Hong Kong or elsewhere), which is directed at, or the contents of which are likely to be accessed or read by, the public in Hong Kong (except if permitted to do so under the laws of Hong Kong) other than with respect to shares which are or are intended to be disposed of only to persons outside Hong Kong or only to “professional investors” within the meaning of the Securities and Futures Ordinance (Cap. 571, Laws of Hong Kong) and any rules made thereunder.

Notice to Prospective Investors in Japan

The shares offered in this prospectus supplement have not been and will not be registered under the Financial Instruments and Exchange Law of Japan. The shares have not been offered or sold and will not be

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offered or sold, directly or indirectly, in Japan or to or for the account of any resident of Japan (including any corporation or other entity organized under the laws of Japan), except (i) pursuant to an exemption from the registration requirements of the Financial Instruments and Exchange Law and (ii) in compliance with any other applicable requirements of Japanese law.

Notice to Prospective Investors in Singapore

This prospectus supplement has not been registered as a prospectus with the Monetary Authority of Singapore. Accordingly, this prospectus supplement and any other document or material in connection with the offer or sale, or invitation for subscription or purchase, of the shares may not be circulated or distributed, nor may the shares be offered or sold, or be made the subject of an invitation for subscription or purchase, whether directly or indirectly, to persons in Singapore other than (i) to an institutional investor under Section 274 of the Securities and Futures Act, Chapter 289 of Singapore (the “SFA”), (ii) to a relevant person pursuant to Section 275(1), or any person pursuant to Section 275(1A), and in accordance with the conditions specified in Section 275 of the SFA or (iii) otherwise pursuant to, and in accordance with the conditions of, any other applicable provision of the SFA, in each case subject to compliance with conditions set forth in the SFA.

Where the shares are subscribed or purchased under Section 275 of the SFA by a relevant person which is:

•

a corporation (which is not an accredited investor (as defined in Section 4A of the SFA)) the sole business of which is to hold investments and the entire share capital of which is owned by one or more individuals, each of whom is an accredited investor; or

•

a trust (where the trustee is not an accredited investor) whose sole purpose is to hold investments and each beneficiary of the trust is an individual who is an accredited investor,

shares, debentures and units of shares and debentures of that corporation or the beneficiaries’ rights and interest (howsoever described) in that trust shall not be transferred within six months after that corporation or that trust has acquired the shares pursuant to an offer made under Section 275 of the SFA except:

•

to an institutional investor (for corporations, under Section 274 of the SFA) or to a relevant person defined in Section 275(2) of the SFA, or to any person pursuant to an offer that is made on terms that such shares, debentures and units of shares and debentures of that corporation or such rights and interest in that trust are acquired at a consideration of not less than S$200,000 (or its equivalent in a foreign currency) for each transaction, whether such amount is to be paid for in cash or by exchange of securities or other assets, and further for corporations, in accordance with the conditions specified in Section 275 of the SFA;

•

where no consideration is or will be given for the transfer; or

•

where the transfer is by operation of law.

Notice to Prospective Investors in Canada

The shares offered in this prospectus supplement may be sold only to purchasers purchasing, or deemed to be purchasing, as principal that are accredited investors, as defined in NationalInstrument 45-106 Prospectus Exemptions or subsection 73.3(1) of the Securities Act (Ontario), and are permitted clients, as defined in NationalInstrument 31-103 Registration Requirements, Exemptions and Ongoing Registrant Obligations. Any resale of the securities must be made in accordance with an exemption from, or in a transaction not subject to, the prospectus requirements of applicable securities laws.

Securities legislation in certain provinces or territories of Canada may provide a purchaser with remedies for rescission or damages if this prospectus supplement (including any amendment thereto) contains a misrepresentation, provided that the remedies for rescission or damages are exercised by the purchaser within the

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time limit prescribed by the securities legislation of the purchaser’s province or territory. The purchaser should refer to any applicable provisions of the securities legislation of the purchaser’s province or territory for particulars of these rights or consult with a legal advisor.

Pursuant to section 3A.3 (or, in the case of securities issued or guaranteed by the government ofa non-Canadian jurisdiction, section 3A.4) of NationalInstrument 33-105 Underwriting Conflicts(NI 33-105), the representatives are not required to comply with the disclosure requirements ofNI 33-105 regarding underwriter conflicts of interest in connection with this offering.

Notice to Prospective Investors in the State of Israel

In the State of Israel this prospectus shall not be regarded as an offer to the public to purchase shares of common stock under the Israeli Securities Law, 5728-1968, which requires a prospectus to be published and authorized by the Israel Securities Authority, if it complies with certain provisions of Section 15 of the Israeli Securities Law, 5728-1968, including, inter alia, if: (1) the offer is made, distributed or directed to not more than 35 investors, subject to certain conditions, or the Addressed Investors; or (2) the offer is made, distributed or directed to certain qualified investors defined in the First Addendum of the Israeli Securities Law, 5728-1968, subject to certain conditions, or Qualified Investors. The Qualified Investors shall not be taken into account in the count of the Addressed Investors and may be offered to purchase securities in addition to the 35 Addressed Investors. We have not and will not take any action that would require us to publish a prospectus in accordance with and subject to the Israeli Securities Law, 5728-1968. We have not and will not distribute this prospectus or make, distribute or direct an offer to subscribe for our common stock to any person within the State of Israel, other than to Qualified Investors and up to 35 Addressed Investors.

Qualified Investors may have to submit written evidence that they meet the definitions set out in of the First Addendum to the Israeli Securities Law, 5728-1968. In particular, we may request that Qualified Investors will each represent, warrant and certify to us and/or to anyone acting on our behalf: (1) that it is an investor falling within one of the categories listed in the First Addendum to the Israeli Securities Law, 5728-1968; (2) which of the categories listed in the First Addendum to the Israeli Securities Law, 5728-1968 regarding Qualified Investors is applicable to it; (3) that it will abide by all provisions set forth in the Israeli Securities Law, 5728-1968 and the regulations promulgated thereunder in connection with this offering; (4) that the shares of common stock that it will be issued are, subject to exemptions available under the Israeli Securities Law, 5728-1968: (a) for its own account; (b) for investment purposes only; and (c) not issued with a view to resale within the State of Israel, other than in accordance with the provisions of the Israeli Securities Law, 5728-1968; and (5) that it is willing to provide further evidence of its Qualified Investor status. Addressed Investors may have to submit written evidence in respect of their identity and may have to sign and submit a declaration containing, inter alia, the Addressed Investor’s name, address and passport number or Israeli identification number.

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EXPENSES

The following is an estimate of the expenses (all of which are to be paid by us) that we expect to incur in connection with this offering.


SEC registration fee*	$	9,090
FINRA fee	$	11,750
Printing expenses	$	12,000
Legal fees and expenses	$	272,000
Accounting fees and expenses	$	135,000
Transfer agent fees and expenses	$	5,000
Miscellaneous	$	10,160

Total	$	450,000

*	Previously paid in connection with our registration statement on FormF-3 (FileNo. 333-233367) filed on August 20, 2019.

LEGAL MATTERS

The validity of our common shares offered hereby and certain other matters of Dutch law will be passed upon for us by NautaDutilh N.V. and certain matters of U.S. federal law will be passed upon for us by Latham & Watkins LLP. Cooley LLP, New York, New York is counsel to the underwriters in connection with this offering.

EXPERTS

The consolidated financial statements of Merus N.V. as of December 31, 2018 and 2017, and for each of the years in the three-year period ended December 31, 2018, included in the Annual Report on Form20-F filed by Merus N.V. on April 3, 2019, have been incorporated by reference herein and in the registration statement of which this prospectus forms a part in reliance upon the report of KPMG Accountants N.V., independent registered public accounting firm, incorporated by reference herein, and upon the authority of said firm as experts in accounting and auditing. The audit report refers to the adoption of International Financial Reporting Standard 15Revenue from Contracts with Customers. The registered offices of KPMG Accountants N.V. are located at Laan van Langerhuize 1, 1186 DS Amstelveen, the Netherlands.

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WHERE YOU CAN FIND MORE INFORMATION; INCORPORATION BY REFERENCE

Available Information

We are subject to the periodic reporting and other informational requirements of the Securities Exchange Act of 1934, or the Exchange Act. Under the Exchange Act, we file annual reports and other information with the SEC. As a foreign private issuer, we are exempt from, among other things, the rules under the Exchange Act prescribing the furnishing and content of proxy statements and our officers, directors and principal shareholders are exempt from the reporting and short-swing profit recovery provisions contained in Section 16 of the Exchange Act.

The SEC maintains an internet site that contains reports, proxy and information statements, and other information regarding issuers, such as us, that file electronically with the SEC atwww.sec.gov. Our internet address iswww.merus.nl. The information contained on, or that can be accessed through, our website is not a part of, and shall not be incorporated by reference into, this prospectus. We have included our internet address as an inactive textual reference only.

This prospectus supplement and the accompanying prospectus are part of a registration statement that we filed with the SEC and do not contain all of the information in the registration statement. The full registration statement may be obtained from the SEC or us, as provided below. Forms of the documents establishing the terms of the offered securities are or may be filed as exhibits to the registration statement of which this prospectus supplement and the accompanying prospectus form a part. Statements in this prospectus supplement and the accompanying prospectus about these documents are summaries and each statement is qualified in all respects by reference to the document to which it refers. You should refer to the actual documents for a more complete description of the relevant matters. You may inspect a copy of the registration statement at the SEC’s website, as provided above.

Incorporation by Reference

The SEC’s rules allow us to “incorporate by reference” information into this prospectus supplement, which means that we can disclose important information to you by referring you to another document filed separately with the SEC. The information incorporated by reference is deemed to be part of this prospectus supplement, and subsequent information that we file with the SEC will automatically update and supersede that information. Any statement contained in a previously filed document incorporated by reference will be deemed to be modified or superseded for purposes of this prospectus supplement to the extent that a statement contained in this prospectus supplement modifies or replaces that statement.

This prospectus supplement incorporates by reference the documents set forth below that have previously been filed with the SEC:

•

Our Annual Report onForm20-F for the year ended December 31, 2018, filed with the SEC on April 3, 2019.

•

Our Reports on Form6-K filed with the SEC onMay 23, 2019 (excluding Exhibit 2 thereto),June 14, 2019,July 31, 2019, Exhibit 1 to our Report on Form6-K filed with the SEC onAugust 19, 2019, and our report on Form6-K filed with the SEC on November 4, 2019.

•

The description of our common shares contained in our registration statement onForm8-A filed with the SEC on May 11, 2016, including any amendments or reports filed for the purpose of updating such description.

We are also incorporating by reference all subsequent annual reports on Form20-F that we file with the SEC, which shall be deemed incorporated by reference into this prospectus supplement when filed, and certain reports on Form6-K that we furnish to the SEC after the date of this prospectus supplement (if they state that they are incorporated by reference) prior to the termination of this offering. In all cases, you should rely on the later information over different information included in this prospectus supplement.

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Unless expressly incorporated by reference, nothing in this prospectus supplement shall be deemed to incorporate by reference information furnished to, but not filed with, the SEC. Copies of all documents incorporated by reference in this prospectus supplement, other than exhibits to those documents unless such exhibits are specifically incorporated by reference in this prospectus supplement, will be provided at no cost to each person, including any beneficial owner, who receives a copy of this prospectus supplement on the written or oral request of that person made to:

Merus N.V.

Yalelaan 62

3584 CM Utrecht

The Netherlands

+31 85 016 2500

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PROSPECTUS

LOGO

$250,000,000

Common Shares

Preferred Shares

Warrants

Units

We may offer and sell up to $250,000,000 in the aggregate of the securities identified above, in each case from time to time in one or more offerings. This prospectus provides you with a general description of the securities.

Each time we offer and sell or otherwise dispose of the securities described in this prospectus, we will provide a supplement to this prospectus that contains specific information about the offering and the amounts, prices and terms of the securities. The supplement may also add, update or change information contained in this prospectus with respect to the offering. You should carefully read this prospectus and the applicable prospectus supplement before you invest in any of our securities.

We may offer and sell the securities described in this prospectus and any prospectus supplement to or through one or more underwriters, dealers and agents, or directly to purchasers, or through a combination of these methods. If any underwriters, dealers or agents are involved in the sale of any of the securities, their names and any applicable purchase price, fee, commission or discount arrangement between or among them will be set forth, or will be calculable from the information set forth, in the applicable prospectus supplement. See the sections of this prospectus entitled “About this Prospectus” and “Plan of Distribution” for more information. No securities may be sold without delivery of this prospectus and the applicable prospectus supplement describing the method and terms of the offering of such securities.

INVESTING IN OUR SECURITIES INVOLVES RISKS. SEE THE “RISK FACTORS” ON PAGE 3 OF THIS PROSPECTUS AND THE DOCUMENTS INCORPORATED BY REFERENCE INTO THIS PROSPECTUS CONCERNING FACTORS YOU SHOULD CONSIDER BEFORE INVESTING IN OUR SECURITIES.

Our common shares are listed on The Nasdaq Global Market under the symbol “MRUS.” On August 19, 2019, the last reported sale price of our common shares on The Nasdaq Global Market was $18.55 per share.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

The date of this prospectus is August 27, 2019.

TABLE OF CONTENTS



About This Prospectus			1

Presentation of Financial Information			1

About the Company			2

Risk Factors			3

Special Note Regarding Forward-Looking Statements			4

Capitalization and Indebtedness			6

Use of Proceeds			7

Description of Share Capital and Articles of Association			8

Descriptions of Warrants			29

Description of Units			31

Global Securities			32

Plan of Distribution			36

Exchange Controls			38

Material Changes			38

Expenses			38

Legal Matters			38

Experts			38

Enforcement of Civil Liabilities			39

Where You Can Find More Information; Incorporation by Reference			40

Material Contracts			41

ABOUT THIS PROSPECTUS

This prospectus is a part of a registration statement that we filed with the U.S. Securities and Exchange Commission, or the SEC, utilizing a “shelf” registration process. By using a shelf registration statement, we may sell securities from time to time and in one or more offerings up to a total dollar amount of $250,000,000 as described in this prospectus. Each time that we offer and sell securities, we will provide a prospectus supplement to this prospectus that contains specific information about the securities being offered and sold and the specific terms of that offering. The prospectus supplement may also add, update or change information contained in this prospectus with respect to that offering. If there is any inconsistency between the information in this prospectus and the applicable prospectus supplement, you should rely on the prospectus supplement. Before purchasing any securities, you should carefully read both this prospectus and the applicable prospectus supplement, together with the additional information described under the heading “Where You Can Find More Information; Incorporation by Reference.”

You should rely only on the information contained or incorporated by reference in this prospectus, any prospectus supplement and any issuer free writing prospectus. We have not authorized any other person to provide you with different information or to make any representation other than those contained or incorporated by reference in this prospectus. If any person provides you with different or inconsistent information, you should not rely on it. We will not make an offer to sell these securities in any jurisdiction where the offer or sale is not permitted. You should assume that the information appearing in this prospectus and the applicable prospectus supplement to this prospectus is accurate as of the date on its respective cover, and that any information incorporated by reference is accurate only as of the date of the document incorporated by reference, unless we indicate otherwise. Our business, financial condition, results of operations and prospects may have changed since those dates.

PRESENTATION OF FINANCIAL INFORMATION

We report under International Financial Reporting Standards, or IFRS, as issued by the International Accounting Standards Board, or the IASB. None of the financial statements presented or incorporated by reference in this prospectus were prepared in accordance with generally accepted accounting principles in the United States. We present our financial statements in euros and in accordance with IFRS as issued by the IASB. We have made rounding adjustments to some of the figures included in this prospectus. Accordingly, numerical figures shown as totals in some tables may not be an arithmetic aggregation of the figures that preceded them. All references in this prospectus to “$” and “U.S. dollars” mean U.S. dollars and all references to “€” mean euros, unless otherwise noted.

ABOUT THE COMPANY

We are a clinical-stage immuno-oncology company developing innovative bispecific antibody therapeutics. Our pipeline of full-length human bispecific antibody candidates, which we refer to as Biclonics^®, are generated from our Biclonics^® technology platform, which is able to generate a diverse array of antibody-heavy chains against virtually any target, paired with a common light chain. Two heavy chains paired with a common light chain can be combined to produce novel bispecific antibodies that bind to a diverse array of targets and display differentiated biology. By binding to two different targets, Biclonics^® can provide a variety of mechanisms of action. We are developingMCLA-128 for the treatment of HER2-expressing solid tumors and other solid tumors,MCLA-117 for the treatment of acute myeloid leukemia,MCLA-158 for the potential treatment of solid tumors andMCLA-145, which is being developed in collaboration with Incyte Corporation, for the potential treatment of solid tumors. We also have a pipeline of proprietary antibody candidates in preclinical development.

Our principal executive offices are located at Yalelaan 62, 3584 CM Utrecht, the Netherlands. Our telephone number at this address is +31 30 253 8800.

We are an “emerging growth company,” as defined in the Jumpstart Our Business Startups Act of 2012. We will remain an emerging growth company until the earlier of (1) the last day of the fiscal year following the fifth anniversary of the completion of our initial public offering of our common shares, (2) the last day of the fiscal year in which we have total annual gross revenue of at least $1.07 billion, (3) the last day of the fiscal year in which we are deemed to be a large accelerated filer, which will occur when the market value of our common shares held bynon-affiliates exceeds $700 million as of the end of the second quarter of the fiscal year and (4) the date on which we have issued more than an aggregate of $1.0 billion innon-convertible debt during the prior three-year period.

RISK FACTORS

Investment in any securities offered pursuant to this prospectus involves risks. You should carefully consider the risk factors incorporated by reference from our most recent Annual Report on Form20-F and any subsequent Annual Reports on Form20-F we file after the date of this prospectus, and all other information contained or incorporated by reference into this prospectus or the registration statement of which this prospectus forms a part, as updated by our subsequent filings under the Securities Exchange Act of 1934, as amended, or the Exchange Act, and the risk factors and other information contained in any applicable prospectus supplement, before acquiring any of our securities. The occurrence of any of these risks might cause you to lose all or part of your investment in our securities.

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus and the documents that are incorporated by reference into this prospectus contains statements that constitute forward-looking statements. Many of the forward-looking statements contained in this prospectus and the documents incorporated herein can be identified by the use of forward-looking words such as “anticipate,” “believe,” “could,” “expect,” “should,” “plan,” “intend,” “estimate” and “potential,” among others.

Forward-looking statements appear in a number of places in this prospectus and in the documents incorporated herein include, but are not limited to, statements regarding our intent, belief or current expectations. Forward-looking statements are based on our management’s beliefs and assumptions and on information currently available to our management. Such statements are subject to risks and uncertainties, and actual results may differ materially from those expressed or implied in the forward-looking statements due to various important factors, including, but not limited to, those referenced under the section titled “Risk Factors” in this prospectus. Forward-looking statements include, but are not limited to, statements about:

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our operations as a clinical-stage company with a limited operating history and a history of operating losses;

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uncertainty about the initiation, timing, progress and results of clinical trials of our bispecific antibody candidates, including regarding when results of such trials will be made public;

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our expectations related to payments and clinical development under our collaboration agreement with Incyte Corporation, or Incyte;

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our clinical development plans forMCLA-128,MCLA-117,MCLA-158, andMCLA-145;

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research and/or development of preclinical programs beingco-developed with Incyte, Simcere Pharmaceutical Group, and Betta Pharmaceuticals Co. Ltd, or Betta, and for other bispecific antibody candidates;

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the timing or likelihood of regulatory filings and approvals for any of our bispecific antibody candidates;

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our ability to establish sales, marketing and distribution capabilities for any of our bispecific antibody candidates for which we may obtain regulatory approval;

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our ability to establish and maintain manufacturing arrangements for our bispecific antibody candidates;

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the scope of protection we are able to establish and maintain for intellectual property rights covering our bispecific antibody candidates and related technology;

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our ability to defend against any claims by third parties that we are infringing upon their intellectual property rights;

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our estimates regarding expenses, future revenues, capital requirements and our need for additional financing;

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the rate and degree of market acceptance of our bispecific antibody candidates;

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the impact of government laws and regulations on our business;

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our competitive position; and

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other risk factors under “Risk Factors” in this prospectus or included in the documents incorporated by reference into this prospectus.

You should read this prospectus and the documents incorporated by reference in this prospectus completely and with the understanding that our actual results may differ materially from what we expect as expressed or implied by our forward-looking statements. In light of the significant risks and uncertainties to which our forward-looking statements are subject, you should not place undue reliance on or regard these statements as a representation or warranty by us or any other person that we will achieve our objectives and plans in any specified timeframe, or at all. We discuss many of these risks in greater detail in the documents incorporated by reference into this prospectus. For all forward-looking statements, we claim the protection of the safe harbor for forward-looking statements contained in the Private Securities Litigation Reform Act of 1995.

CAPITALIZATION AND INDEBTEDNESS

The following table sets forth our cash and cash equivalents and capitalization as of June 30, 2019 derived from our unaudited financial statements incorporated by reference into this prospectus:


(euro in thousands)
Cash and cash equivalents	€	131,993

Shareholders’ equity:
Issued capital:
Common shares		2,105
Share premium		264,878
Accumulated loss		(190,214	)

Total equity (deficit)		76,769

Total capitalization	€	76,769

The table above excludes:

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3,282,510 common shares issuable upon the exercise of share options outstanding as of June 30, 2019 at a weighted average exercise price of €13.27 per share;

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76,972 common shares issuable upon the vesting of restricted share units outstanding as of June 30, 2019; and

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USE OF PROCEEDS

We intend to use the net proceeds from the sale of the securities as set forth in the applicable prospectus supplement.

DESCRIPTION OF SHARE CAPITAL AND ARTICLES OF ASSOCIATION

Set forth below is a summary of certain information concerning our share capital as well as a description of certain provisions of our articles of association and relevant provisions of Dutch law. Because the following is only a summary, it does not contain all of the information that may be important to you. The summary includes certain references to and descriptions of material provisions of our articles of association and Dutch law in effect as of the date of this prospectus. The summary below does not purport to be complete and is qualified in its entirety by reference to applicable Dutch law and our articles of association, which is filed as an exhibit to the registration statement of which this prospectus is a part.

General

We were incorporated on June 16, 2003 as a private company with limited liability (besloten vennootschap met beperkte aansprakelijkheid) under Dutch law. In connection with the initial public offering of our common shares, we converted into a Dutch public company with limited liability (naamloze vennootschap).

We are registered with the Dutch Trade Register (handelsregister) under number 30189136. Our corporate seat is in Utrecht, the Netherlands, and our registered office is Yalelaan 62, 3584 CM Utrecht, the Netherlands.

Share Capital

Common Shares

Preferred Shares

History of Share Capital

Since January 1, 2016, our issued share capital has changed as provided below.

On March 16, 2016, we issued 12,107 common shares upon the exercise of options by the former Chairman of our board of directors (through the STAK) for aggregate consideration of €23,317 in cash.

On May 6, 2016, we effected a1-for-1.80 reverse share split of our common shares and all classes of our preferred shares issued at that time.

and we issued a total of 1,312,718 common shares to holders of our preferred shares in satisfaction of accrued and unpaid dividends.