7. Segment Information and Concentration of Business Risk

We have two reportable segments Ionis Core and Akcea Therapeutics. Prior to Akcea’s IPO in July 2017, we owned 100 percent of Akcea. From the closing of Akcea’s IPO in July 2017 through mid-April 2018, we owned approximately 68 percent of Akcea. In April 2018, we received eight million shares of Akcea’s stock when we licensed TEGSEDI and AKCEA-TTR-L_Rx to Akcea and we purchased an additional 10.7 million shares of Akcea’s stock for $200 million, increasing our ownership percentage to approximately 75 percent. In August 2018, we received an additional 1.6 million shares of Akcea’s stock when TEGSEDI was approved in the EU. 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 six months ended June 30, 2018 and 2017 (in thousands), respectively.

Three Months Ended June 30, 2018	Ionis Core		Akcea Therapeutics			Elimination of Intercompany Activity			Total
Revenue:
Commercial revenue:
SPINRAZA royalties	$	56,653	$	—		$	—		$	56,653
Licensing and other royalty revenue		545		—			—			545
Total commercial revenue		57,198		—			—			57,198
R&D revenue under collaborative agreements		42,228		18,321			—			60,549
Total segment revenue	$	99,426	$	18,321		$	—		$	117,747
Total operating expenses	$	85,875	$	81,744		$	409		$	168,028
Income (loss) from operations	$	13,551	$	(63,423	)	$	(409	)	$	(50,281	)

Three Months Ended June 30, 2017 (as revised)	Ionis Core		Akcea Therapeutics			Elimination of Intercompany Activity			Total
Revenue:
Commercial revenue:
SPINRAZA royalties	$	22,366	$	—		$	—		$	22,366
Licensing and other royalty revenue		1,322		—			—			1,322
Total commercial revenue		23,688		—			—			23,688
R&D revenue under collaborative agreements		85,802		5,713			(2,930	)		88,585
Total segment revenue	$	109,490	$	5,713		$	(2,930	)	$	112,273
Total operating expenses	$	83,381	$	25,402		$	(2,960	)	$	105,823
Income (loss) from operations	$	26,109	$	(19,689	)	$	30		$	6,450

Six Months Ended June 30, 2018	Ionis Core		Akcea Therapeutics			Elimination of Intercompany Activity			Total
Revenue:
Commercial revenue:
SPINRAZA royalties	$	97,734	$	—		$	—		$	97,734
Licensing and other royalty revenue		1,487		—			—			1,487
Total commercial revenue		99,221		—			—			99,221
R&D revenue under collaborative agreements		132,744		35,429			(5,229	)		162,944
Total segment revenue	$	231,965	$	35,429		$	(5,229	)	$	262,165
Total operating expenses	$	191,419	$	129,179		$	(4,850	)	$	315,748
Income (loss) from operations	$	40,546	$	(93,750	)	$	(379	)	$	(53,583	)

Six Months Ended June 30, 2017 (as revised)	Ionis Core		Akcea Therapeutics			Elimination of Intercompany Activity			Total
Revenue:
Commercial revenue:
SPINRAZA royalties	$	27,577	$	—		$	—		$	27,577
Licensing and other royalty revenue		3,912		—			—			3,912
Total commercial revenue		31,489		—			—			31,489
R&D revenue under collaborative agreements		239,184		11,807			(54,407	)		196,584
Total segment revenue	$	270,673	$	11,807		$	(54,407	)	$	228,073
Total operating expenses	$	161,733	$	94,872		$	(54,467	)	$	202,138
Income (loss) from operations	$	108,940	$	(83,065	)	$	60		$	25,935

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

Total Assets	Ionis Core		Akcea Therapeutics		Elimination of Intercompany Activity			Total
June 30, 2018	$	2,351,098	$	395,005	$	(498,788	)	$	2,247,315
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 June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
				(as revised)				(as revised)
Partner A		66 %		72 %		50 %		48 %
Partner B		16 %		5 %		14 %		5 %
Partner C		3 %		4 %		28 %		4 %
Partner D		5 %		11 %		2 %		6 %
Partner E		1%		0%		1%		29%

Contracts receivables from four significant partners comprised approximately 92 percent of our contracts receivables at June 30, 2018. Contracts receivables from two significant partners comprised approximately 84 percent of our contracts receivables at December 31, 2017.