7. Segment Information and Concentration of Business Risk

We have two reportable segments Ionis Core and Akcea Therapeutics. At September 30, 2018 we owned approximately 75 percent of Akcea. In October 2018, we received an additional 1.7 million shares of Akcea’s stock when TEGSEDI was approved by the FDA, increasing our ownership percentage to 76 percent. Segment income (loss) from operations includes revenue less operating expenses attributable to each segment.

In our Ionis Core segment we are exploiting our antisense technology to generate a broad pipeline of first-in-class and/or best-in-class drugs for us and our partners. Our Ionis Core segment generates revenue from a multifaceted partnering strategy.

Akcea is a biopharmaceutical company focused on developing and commercializing drugs to treat patients with rare and serious diseases.

The following tables show our segment revenue and income (loss) from operations for the three and nine months ended September 30, 2018 and 2017 (in thousands), respectively.

Three Months Ended September 30, 2018	Ionis Core		Akcea Therapeutics			Elimination of Intercompany Activity			Total
Revenue:
Commercial revenue:
SPINRAZA royalties	$	70,010	$	—		$	—		$	70,010
Licensing and other royalty revenue		7,946		12,000			(7,200	)		12,746
Total commercial revenue		77,956		12,000			(7,200	)		82,756
R&D revenue under collaborative agreements		100,105		7,241			(44,707	)		62,639
Total segment revenue	$	178,061	$	19,241		$	(51,907	)	$	145,395
Total operating expenses	$	87,664	$	84,249		$	(7,946	)	$	163,967
Income (loss) from operations	$	90,397	$	(65,008	)	$	(43,961	)	$	(18,572	)

Three Months Ended September 30, 2017 (as revised)	Ionis Core		Akcea Therapeutics			Elimination of Intercompany Activity			Total
Revenue:
Commercial revenue:
SPINRAZA royalties	$	32,890	$	—		$	—		$	32,890
Licensing and other royalty revenue		1,727		—			—			1,727
Total commercial revenue		34,617		—			—			34,617
R&D revenue under collaborative agreements		73,791		9,906			—			83,697
Total segment revenue	$	108,408	$	9,906		$	—		$	118,314
Total operating expenses	$	81,019	$	26,013		$	(30	)	$	107,002
Income (loss) from operations	$	27,389	$	(16,107	)	$	30		$	11,312

Nine Months Ended September 30, 2018	Ionis Core		Akcea Therapeutics			Elimination of Intercompany Activity			Total
Revenue:
Commercial revenue:
SPINRAZA royalties	$	167,743	$	—		$	—		$	167,743
Licensing and other royalty revenue		9,432		12,000			(7,200	)		14,232
Total commercial revenue		177,175		12,000			(7,200	)		181,975
R&D revenue under collaborative agreements		232,850		42,670			(49,936	)		225,584
Total segment revenue	$	410,025	$	54,670		$	(57,136	)	$	407,559
Total operating expenses	$	279,084	$	213,428		$	(12,796	)	$	479,716
Income (loss) from operations	$	130,941	$	(158,758	)	$	(44,340	)	$	(72,157	)

Nine Months Ended September 30, 2017 (as revised)	Ionis Core		Akcea Therapeutics			Elimination of Intercompany Activity			Total
Revenue:
Commercial revenue:
SPINRAZA royalties	$	60,467	$	—		$	—		$	60,467
Licensing and other royalty revenue		5,639		—			—			5,639
Total commercial revenue		66,106		—			—			66,106
R&D revenue under collaborative agreements		312,976		21,712			(54,407	)		280,281
Total segment revenue	$	379,082	$	21,712		$	(54,407	)	$	346,387
Total operating expenses	$	242,753	$	120,884		$	(54,497	)	$	309,140
Income (loss) from operations	$	136,329	$	(99,172	)	$	90		$	37,247

The following table shows our total assets by segment at September 30, 2018 and December 31, 2017 (in thousands), respectively.

Total Assets	Ionis Core		Akcea Therapeutics		Elimination of Intercompany Activity			Total
September 30, 2018	$	2,446,425	$	379,128	$	(577,641	)	$	2,247,913
December 31, 2017 (as revised)	$	1,342,578	$	268,804	$	(288,608	)	$	1,322,774

We have historically funded our operations from collaborations with corporate partners and a relatively small number of partners have accounted for a significant percentage of our revenue. Revenue from significant partners, which is defined as ten percent or more of our total revenue, was as follows:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
				(as revised)				(as revised)
Partner A		72%		74%		58%		57%
Partner B		10%		4%		21%		4%
Partner C		5%		8%		10%		6%
Partner D		8%		0%		3%		0%
Partner E		1%		0%		1%		19%

Contracts receivables from two significant partners comprised approximately 84 percent of our contracts receivables at September 30, 2018 and December 31, 2017.