United states securities and exchange commission

Table of Contents
BIOGEN INC. AND SUBSIDIARIES
NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)
F- 28
Long-term inventory, which primarily consists of work in process, is included in investments and other assets in 
our consolidated balance sheets.
Inventory amounts written down as a result of excess, obsolescence, unmarketability or other reasons are 
charged to cost of sales, and totaled $76.9 million, $48.2 million and $41.9 million for the years ended 
December 31, 2017, 2016 and 2015, respectively. 
7.      Intangible Assets and Goodwill
Intangible Assets
Intangible assets, net of accumulated amortization, impairment charges and adjustments are summarized as 
follows:
 
 
As of December 31, 2017
As of December 31, 2016
(In millions)
Estimated Life
Cost
Accumulated
Amortization
Net
Cost
Accumulated
Amortization
Net
Out-licensed patents
13-23 years
$ 543.3 $ (535.6) $
7.7
$ 543.3 $ (523.6) $
19.7
Developed technology
15-23 years
3,005.3
(2,689.0)
316.3
3,005.3
(2,634.3)
371.0
In-process research
and development
Indefinite until
commercialization
680.6
—
680.6
648.0
—
648.0
Trademarks and trade
names
Indefinite
64.0
—
64.0
64.0
—
64.0
Acquired and in-
licensed rights and
patents
4-18 years
3,971.4
(1,160.4)
2,811.0
3,481.7
(776.1)
2,705.6
Total intangible
assets
$8,264.6 $ (4,385.0) $3,879.6
$7,742.3 $ (3,934.0) $3,808.3
Amortization of acquired intangible assets totaled $814.7 million, $385.6 million and $382.6 million for the 
years ended December 31, 2017, 2016 and 2015, respectively. 
Amortization of acquired intangible assets for the year ended December 31, 2017, includes $444.2 million of 
amortization and impairment charges related to our U.S. and rest of world licenses to Forward Pharma's intellectual 
property, including Forward Pharma's intellectual property related to TECFIDERA, as discussed below. Amortization of 
acquired intangible assets for 2017 also reflects a $31.2 million impairment charge related to the Article 20 
Procedure of ZINBRYTA in the E.U. For additional information on the Article 20 Procedure of ZINBRYTA and resulting 
impairment of ZINBRYTA related assets, please read Note 20, Collaborative and Other Relationships, to these 
consolidated financial statements. 
Balances in the table above as of December 31, 2017 also reflect the elimination of certain amounts 
transferred to Bioverativ in connection with the completion of the spin-off of our hemophilia business. For additional 
information on the spin-off of our hemophilia business, please read Note 3, Hemophilia Spin-Off, to these 
consolidated financial statements. In-process research and development balances include adjustments related to 
foreign currency exchange rate fluctuations.
Out-licensed Patents
Out-licensed patents to third-parties primarily relate to patents acquired in connection with the merger of 
Biogen, Inc. and IDEC Pharmaceuticals Corporation in 2003. 
Developed Technology
Developed technology primarily relates to our AVONEX product, which was recorded in connection with the 
merger of Biogen, Inc. and IDEC Pharmaceuticals Corporation in 2003. The net book value of this asset as of 
December 31, 2017 was $309.5 million. 

---

Table of Contents
BIOGEN INC. AND SUBSIDIARIES
NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)
F- 29
IPR&D
IPR&D represents the fair value assigned to research and development assets that we acquired and had not 
reached technological feasibility at the date of acquisition. Upon commercialization, we will determine the estimated 
useful life and amortize these amounts based upon an economic consumption method. The carrying value 
associated with our IPR&D assets as of December 31, 2017 and 2016 relates to the various IPR&D programs we 
acquired in connection with our acquisitions of Convergence, Stromedix Inc. (Stromedix) and Biogen International 
Neuroscience GmbH (BIN) in 2015, 2012 and 2010, respectively. These amounts have and will be adjusted for 
foreign exchange rate fluctuations. 
An analysis of anticipated lifetime revenues and anticipated development costs is performed annually during 
our long-range planning cycle, which was updated in the third quarter of 2017. This analysis is based upon certain 
assumptions that we evaluate on a periodic basis, including anticipated future product sales, the expected impact of 
changes in the amount of development costs and the probabilities of our programs succeeding, the introduction of 
new products by our competitors and changes in our commercial and pipeline product candidates.   
Acquired and In-licensed Rights and Patents
Acquired and in-licensed rights and patents primarily relate to our acquisition of all remaining rights to TYSABRI 
from Elan. The net book value of this asset as of December 31, 2017 was $2,236.2 million. 
The net change in acquired and in-licensed rights and patents during 2017 reflects $90.0 million in total 
milestone payments paid to Ionis Pharmaceuticals, Inc. (Ionis) for the approvals of SPINRAZA in the E.U. and Japan 
in June 2017 and July 2017, respectively, the $25.0 million milestone payment paid to Samsung Bioepis, for the 
approval of IMRALDI, an adalimumab biosimilar referencing HUMIRA, in the E.U. in August 2017, and the net carrying 
value recognized in relation to our acquisition of TECFIDERA license rights, as described below. These net increases 
were in part offset by amortization and the $31.2 million impairment charge related to the Article 20 Procedure of 
ZINBRYTA.
For additional information on our relationships with Ionis and Samsung Bioepis and the European Commission (EC) 
approved restrictions on the use of ZINBRYTA, please read Note 20, Collaborative and Other Relationships, to these 
consolidated financial statements.
TECFIDERA License Rights
In January 2017 we entered into a settlement and license agreement among Biogen Swiss Manufacturing 
GmbH, Biogen International Holding Ltd., Forward Pharma and certain related parties, which was effective as of 
February 1, 2017. Pursuant to this agreement, we obtained U.S. and rest of world licenses to Forward Pharma's 
intellectual property, including Forward Pharma's intellectual property related to TECFIDERA. In exchange, we paid 
Forward Pharma $1.25 billion in cash. During the fourth quarter of 2016, we recognized a pre-tax charge of $454.8 
million related to this agreement and in the first quarter of 2017 we recognized an intangible asset of $795.2 million 
related to this agreement. The pre-tax charge recognized in the fourth quarter of 2016 represented the fair value of 
our license to Forward Pharma’s intellectual property for the period April 2014, when we started selling TECFIDERA, 
through December 31, 2016. The intangible asset represented the fair value of the U.S. and rest of world licenses to 
Forward Pharma’s intellectual property related to TECFIDERA revenues for the period January 2017, the month in 
which we entered into this agreement, through December 2020, the last month before royalty payments could first 
commence pursuant to this agreement. 
We have two intellectual property disputes with Forward Pharma, one in the U.S. and one in the E.U., concerning 
intellectual property related to TECFIDERA. In March 2017 the U.S. intellectual property dispute was decided in our 
favor. Forward Pharma appealed to the U.S. Court of Appeals for the Federal Circuit and the appeal is pending. We 
evaluated the recoverability of the U.S. asset acquired from Forward Pharma and recorded an impairment charge in 
the first quarter of 2017 to adjust the carrying value of the acquired U.S. asset to fair value reflecting the impact of 
the developments in the U.S. legal dispute. In January 2018 the European Patent Office (EPO) announced its 
decision revoking Forward Pharma’s European Patent No. 2 801 355. Forward Pharma has stated that it expects to 
file an appeal to the Technical Board of Appeal of the EPO. Based upon our assessment of these rulings, we continue 
to amortize the remaining net book value of the U.S. and rest of world intangible assets in our consolidated 
statements of income utilizing an economic consumption model.
For additional information on these disputes, please read Note 21, Litigation, to these consolidated financial 
statements.

---