United states securities and exchange commission

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BIOGEN INC. AND SUBSIDIARIES
NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)
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For the years ended December 31, 2017 and 2016, we recognized product revenues totaling $883.7 million 
and $4.6 million, respectively, on our sales of SPINRAZA. Under our agreement with Ionis, we make royalty payments 
to Ionis on annual worldwide net sales of SPINRAZA using a tiered royalty rate between 11% and 15%, which are 
recognized in cost of sales within our consolidated statements of income. Royalty cost of sales related to sales of 
SPINRAZA for the years ended December 31, 2017 and 2016 totaled $112.4 million and $0.5 million, respectively.
Upon entering into this agreement, we made an upfront payment of $29.0 million to Ionis. In addition, during 
2017 we made milestone payments to Ionis totaling $150.0 million related to the marketing approvals discussed 
above, which were capitalized in intangible assets, net in our consolidated balance sheets. During the third quarter 
of 2016, upon the exercise of our option to develop and commercialize SPINRAZA, we also paid a $75.0 million 
license fee to Ionis, which was recognized as research and development expense in our consolidated statements of 
income. 
During 2017 no clinical trial payments were made to Ionis due to the completion of study activities. During 
2016 and 2015, we made clinical trial payments of $35.3 million and $42.8 million, respectively, related to the 
advancement of the program, which were recorded in investments and other assets in our consolidated balance 
sheets as they represented prepaid research and development expenditures. As of December 31, 2017, these 
prepaid research and development amounts were fully expensed as the services were provided.
For the years ending December 31, 2017, 2016 and 2015, $234.5 million, $257.8 million and $74.9 million, 
respectively, were reflected in total costs and expenses in our consolidated statements of income related to the 
advancement and commercialization of the program. 
Antisense Therapeutics
In December 2012 we entered into an agreement with Ionis for the development and commercialization of up 
to three therapeutic targets. 
Under this agreement, Ionis is responsible for global development of any product candidate
 
through the 
completion of a Phase 2 trial and we will provide advice on the clinical trial design and regulatory strategy. We have 
an option to license the product candidate
 
until completion of the Phase 2 trial. If we exercise our option, we will pay 
a license fee of up to $70.0 million to Ionis and assume global development, regulatory and commercialization 
responsibilities. Ionis is eligible to receive up to another $130.0 million in milestone payments upon the 
achievement of certain regulatory milestones as well as royalties on future sales
 
if we successfully develop the 
product candidate after option exercise. 
Upon entering into this agreement, we made an upfront payment of $30.0 million to Ionis and agreed to make 
potential additional payments, prior to licensing, of up to $10.0 million based on the development of the selected 
product candidate as well as a mark-up of the cost estimate of the Phase 1 and Phase 2 trials. During 2015 we 
recognized this $10.0 million developmental milestone upon the selection of BIIB080 (also known as IONIS-MAPT
Rx
), 
which is currently in Phase 1 development. 
Research Collaborations
2013 Long-term Strategic Research Agreement
In September 2013 we entered into a six-year research collaboration agreement with Ionis under which both 
companies collaborate to perform discovery level research and subsequent development and commercialization 
activities of antisense or other therapeutics for the treatment of neurological disorders. Under the collaboration, 
Ionis will perform research on a set of neurological targets identified within this agreement. Once the research has 
reached a specific stage of development, we will make a determination whether antisense therapy is the preferred 
approach to developing a therapeutic candidate or whether another modality is preferred. If an antisense approach is 
selected, Ionis will continue development and identify a potential product candidate. If another modality is selected, 
we will assume responsibility for identifying a potential product candidate and assume development responsibility for 
development in that modality. 
Under this agreement, we made an upfront payment of $100.0 million to Ionis, of which $75.0 million was 
recorded as research and development expense representing the value of intellectual property purchased that had 
not reached technological feasibility. We recognized the remaining $25.0 million as prepaid research and discovery 
services, representing the value of the Ionis full time equivalent employee resources required by the collaboration to 
provide research and discovery services over the term of the collaboration. 

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BIOGEN INC. AND SUBSIDIARIES
NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)
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Ionis is also eligible to receive milestone payments, license fees and royalty payments for all product 
candidates developed through this collaboration, with the specific amount dependent upon the modality of the 
product candidate advanced by us. During the years ending December 31, 2017, 2016 and 2015, we triggered 
milestones of $12.0 million, $5.5 million and $20.0 million, respectively, related to the advancement of IONIS-
SOD1
Rx
 for the treatment of ALS and other neurological targets identified.
For non-ALS antisense product candidates, Ionis will be responsible for global development through the 
completion of a Phase 2 trial and we will provide advice on the clinical trial design and regulatory strategy. For ALS 
antisense product candidates, we are responsible for global development, clinical trial design and regulatory 
strategy. We have an option to license a product candidate until completion of the Phase 2 trial. If we exercise our 
option, we will pay Ionis up to a $70.0 million license fee and assume global development, regulatory and 
commercialization responsibilities. Ionis could receive additional milestone payments upon the achievement of 
certain regulatory milestones of up to $130.0 million, plus additional amounts related to the cost of clinical trials 
conducted by Ionis under the collaboration, and royalties on future sales if we successfully develop the product 
candidate after option exercise.   
For product candidates using a different modality, we will be responsible for global development through all 
stages and will pay Ionis up to $90.0 million upon the achievement of certain regulatory milestones and royalties on 
future sales if we successfully develop the product candidate. 
2017 SMA Collaboration Agreement
In December 2017 we entered into a new collaboration agreement with Ionis to identify new antisense 
oligonucleotide drug candidates for the treatment of SMA. Under this agreement, we will have the option to license 
therapies arising out of this collaboration and will be responsible for their development and commercialization of 
these therapies.
Upon entering into this agreement, we made a $25.0 million upfront payment to Ionis and we may pay Ionis up 
to $260.0 million in additional development and regulatory milestone payments if new drugs advance to marketing 
approval. Upon commercialization, we may also pay Ionis up to $800.0 million in additional performance-based 
milestone payments and tiered royalties on potential net sales of such therapies.
Eisai Co., Ltd. 
BAN2401 and E2609 Collaboration
In March 2014 we entered into a collaboration agreement with Eisai (Eisai Collaboration Agreement) to jointly 
develop and commercialize two Eisai product candidates for the treatment of AD, BAN2401, a monoclonal antibody 
that targets amyloid-beta aggregates, and E2609, a BACE inhibitor. Under the Eisai Collaboration Agreement, Eisai 
serves as the global operational and regulatory lead for both compounds with all costs, including research, 
development, sales and marketing expenses shared equally by us and Eisai; and following marketing approval in 
major markets, such as the U.S., the E.U. and Japan, we and Eisai would co-promote BAN2401 and E2609 and 
share profits equally. In smaller markets, Eisai will distribute these products and pay us a royalty. In addition, the 
Eisai Collaboration Agreement provides both parties with certain rights and obligations in the event of a change in 
control of either party.
The Eisai Collaboration Agreement also provided Eisai with an option to jointly develop and commercialize 
aducanumab (Aducanumab Option) and an option to jointly develop and commercialize one of our anti-tau 
monoclonal antibodies (Anti-Tau Option). Upon exercise of each of the Aducanumab Option and the Anti-Tau Option, a 
separate collaboration agreement would be entered into with Eisai on terms and conditions that mirror the Eisai 
Collaboration Agreement.
In October 2017 Eisai exercised its Aducanumab Option and we entered into a new collaboration agreement for 
the joint development and commercialization of aducanumab (Aducanumab Collaboration Agreement). Eisai has not 
yet exercised its Anti-Tau Option.
Under the Aducanumab Collaboration Agreement, both companies will continue to jointly develop BAN2401 and 
E2609 in accordance with the Eisai Collaboration Agreement; however, we are no longer required to pay Eisai any 
milestone payments for products containing BAN2401 and we are no longer entitled to any potential development 
and commercial milestone payments from Eisai in relation to aducanumab.

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