Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2026	Mar. 31, 2025
Operating activities
Net loss	$ (30,934)	$ (22,647)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	3,629	4,048
Depreciation and impairment of property and equipment	847	749
Non-cash operating lease expense	190	197
Amortization of finance lease right-of-use assets	7	13
Amortization and accretion of premiums/discounts on held-to-maturity investments	(374)	(1,747)
Change in contingent value rights liability	(657)	27
Changes in assets and liabilities:
Prepaid expenses and other current assets	(808)	(278)
Other assets	(45)	79
Accounts payable	2,422	1,694
Accrued expenses and other liabilities	359	(2,203)
Operating lease liabilities	(755)	(706)
Net cash used in operating activities	(26,119)	(20,774)
Investing activities
Purchases of property and equipment	(281)	(780)
Purchases of held-to-maturity investments	(83,479)	(88,965)
Proceeds from maturities of held-to-maturity investments	130,000	44,700
Net cash provided by (used in) investing activities	46,240	(45,045)
Financing activities
Proceeds from the issuance of common stock upon exercise of options	201	19
Principal payments on finance leases	(6)	(15)
Net cash provided by financing activities	195	4
Net increase (decrease) in cash, cash equivalents and restricted cash	20,316	(65,815)
Cash, cash equivalents and restricted cash at beginning of period	104,184	136,925
Cash, cash equivalents and restricted cash at end of period	124,500	71,110
Supplemental disclosure of non-cash investing and financing activities:
Property and equipment included in accounts payable and accrued expenses	354	80
Supplemental cash flow information:
Cash paid for interest	$ 0	$ 2

Increase (Decrease) In Contingent Value Rights Liability

No definition available.

Name:	ngne_IncreaseDecreaseInContingentValueRightsLiability
Namespace Prefix:	ngne_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The sum of the periodic adjustments of the differences between securities' face values and purchase prices that are charged against earnings. This is called accretion if the security was purchased at a discount and amortization if it was purchased at premium. As a noncash item, this element is an adjustment to net income when calculating cash provided by or used in operations using the indirect method.