Convertible preferred stock and stockholders’ equity - Conversion update, Voting rights (Details) $ / shares in Units, $ in Millions	Dec. 11, 2017 USD ($) Vote $ / shares shares	May 04, 2016 Vote $ / shares
Threshold gross proceeds for automatic conversion \| $	$ 70
Threshold share price for automatic conversion	$ 0.446895
Series A Preferred Stock
Number of votes per share \| Vote		1
Number of director entitled to be elected by preferred shareholders \| Vote		4
Series A‑1
Conversion price		$ 0.16472
Series A‑2
Conversion price		$ 0.23061
Series B preferred stock
Conversion price	$ 0.29793
Approval of threshold shares \| shares	30,208,439
Number of votes per share \| Vote	1

Threshold shares from which approval is required for conversion.

No definition available.

Name:	aptx_ConversionOfTemporaryEquityApprovalOfThresholdShares
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Represents the number of director entitled to be elected by preferred shareholders.

No definition available.

Name:	aptx_NumberOfDirectorEntitledToBeElectedByPreferredShareholders
Namespace Prefix:	aptx_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Represents the number of votes per share.

No definition available.

Name:	aptx_NumberOfVotesPerShare
Namespace Prefix:	aptx_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Threshold amount of gross proceeds from underwritten public offering upon which the conversion becomes automatic.

No definition available.

Name:	aptx_TemporaryEquityAutomaticConversionThresholdGrossProceedsOfUnderwrittenPublicOffering
Namespace Prefix:	aptx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Threshold share price upon which the conversion becomes automatic.

No definition available.

Name:	aptx_TemporaryEquityAutomaticConversionThresholdSharePrice
Namespace Prefix:	aptx_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

Represents the conversion price per share of temporary equity.

No definition available.

Name:	aptx_TemporaryEquityConversionPricePerShare
Namespace Prefix:	aptx_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

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Namespace Prefix:
Data Type:	na
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Data Type:	na
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Period Type: