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Summary of Significant Accounting Policies - Concentrations of Credit Risk (Details) | Sep. 30, 2021 Institution
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Summary of Significant Accounting Policies |
Number of financial institutions at which cash is held | 2

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- Definition The number of financial institutions that hold the entity's cash. + References No definition available. + Details
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Namespace Prefix: | ptgx_
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Balance Type: | na
Period Type: | instant

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- References No definition available. + Details
Name: | us-gaap_AccountingPoliciesAbstract
Namespace Prefix: | us-gaap_
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