3.20.2 html 247 389 1 false 68 0 false 5 false false R1.htm 100000 - Document - Document and Entity Information Sheet http://www.mtem.com/20200630/taxonomy/role/DocumentDocumentAndEntityInformation Document and Entity Information Cover 1 false false R2.htm 100010 - Statement - Condensed Consolidated Balance Sheets Sheet http://www.mtem.com/20200630/taxonomy/role/StatementCondensedConsolidatedBalanceSheets Condensed Consolidated Balance Sheets Statements 2 false false R3.htm 100020 - Statement - Condensed Consolidated Balance Sheets (Parenthetical) Sheet http://www.mtem.com/20200630/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsParenthetical Condensed Consolidated Balance Sheets (Parenthetical) Statements 3 false false R4.htm 100030 - Statement - Condensed Consolidated Statements of Operations (Unaudited) Sheet http://www.mtem.com/20200630/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperationsUnaudited Condensed Consolidated Statements of Operations (Unaudited) Statements 4 false false R5.htm 100040 - Statement - Condensed Consolidated Statements of Comprehensive Loss (Unaudited) Sheet http://www.mtem.com/20200630/taxonomy/role/StatementCondensedConsolidatedStatementsOfComprehensiveLossUnaudited Condensed Consolidated Statements of Comprehensive Loss (Unaudited) Statements 5 false false R6.htm 100050 - Statement - Condensed Consolidated Statements of Stockholders' Equity (Deficit) (Unaudited) Sheet http://www.mtem.com/20200630/taxonomy/role/StatementCondensedConsolidatedStatementsOfStockholdersEquityDeficitUnaudited Condensed Consolidated Statements of Stockholders' Equity (Deficit) (Unaudited) Statements 6 false false R7.htm 100060 - Statement - Condensed Consolidated Statements of Cash Flows (Unaudited) Sheet http://www.mtem.com/20200630/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited Condensed Consolidated Statements of Cash Flows (Unaudited) Statements 7 false false R8.htm 100070 - Disclosure - Organization and Summary of Significant Accounting Policies Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureOrganizationAndSummaryOfSignificantAccountingPolicies Organization and Summary of Significant Accounting Policies Notes 8 false false R9.htm 100080 - Disclosure - Net Loss Per Common Share Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureNetLossPerCommonShare Net Loss Per Common Share Notes 9 false false R10.htm 100090 - Disclosure - Research and Development Agreements Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureResearchAndDevelopmentAgreements Research and Development Agreements Notes 10 false false R11.htm 100100 - Disclosure - Related Party Transactions Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureRelatedPartyTransactions Related Party Transactions Notes 11 false false R12.htm 100110 - Disclosure - Marketable Securities and Fair Value Measurements Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureMarketableSecuritiesAndFairValueMeasurements Marketable Securities and Fair Value Measurements Notes 12 false false R13.htm 100120 - Disclosure - Balance Sheet Components Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureBalanceSheetComponents Balance Sheet Components Notes 13 false false R14.htm 100130 - Disclosure - Property and Equipment Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosurePropertyAndEquipment Property and Equipment Notes 14 false false R15.htm 100140 - Disclosure - Borrowing Arrangements Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureBorrowingArrangements Borrowing Arrangements Notes 15 false false R16.htm 100150 - Disclosure - Leases Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureLeases Leases Notes 16 false false R17.htm 100160 - Disclosure - Contractual Commitments Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureContractualCommitments Contractual Commitments Notes 17 false false R18.htm 100170 - Disclosure - Stock-Based Compensation Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureStockBasedCompensation Stock-Based Compensation Notes 18 false false R19.htm 100180 - Disclosure - In-Process Research and Development Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureInProcessResearchAndDevelopment In-Process Research and Development Notes 19 false false R20.htm 100190 - Disclosure - Subsequent Events Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureSubsequentEvents Subsequent Events Notes 20 false false R21.htm 100200 - Disclosure - Organization and Summary of Significant Accounting Policies (Policies) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureOrganizationAndSummaryOfSignificantAccountingPoliciesPolicies Organization and Summary of Significant Accounting Policies (Policies) Policies http://www.mtem.com/20200630/taxonomy/role/DisclosureOrganizationAndSummaryOfSignificantAccountingPolicies 21 false false R22.htm 100210 - Disclosure - Research and Development Agreements (Tables) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureResearchAndDevelopmentAgreementsTables Research and Development Agreements (Tables) Tables http://www.mtem.com/20200630/taxonomy/role/DisclosureResearchAndDevelopmentAgreements 22 false false R23.htm 100220 - Disclosure - Marketable Securities and Fair Value Measurements (Tables) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureMarketableSecuritiesAndFairValueMeasurementsTables Marketable Securities and Fair Value Measurements (Tables) Tables http://www.mtem.com/20200630/taxonomy/role/DisclosureMarketableSecuritiesAndFairValueMeasurements 23 false false R24.htm 100230 - Disclosure - Balance Sheet Components (Tables) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureBalanceSheetComponentsTables Balance Sheet Components (Tables) Tables http://www.mtem.com/20200630/taxonomy/role/DisclosureBalanceSheetComponents 24 false false R25.htm 100240 - Disclosure - Property and Equipment (Tables) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosurePropertyAndEquipmentTables Property and Equipment (Tables) Tables http://www.mtem.com/20200630/taxonomy/role/DisclosurePropertyAndEquipment 25 false false R26.htm 100250 - Disclosure - Borrowing Arrangements (Tables) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureBorrowingArrangementsTables Borrowing Arrangements (Tables) Tables http://www.mtem.com/20200630/taxonomy/role/DisclosureBorrowingArrangements 26 false false R27.htm 100260 - Disclosure - Leases (Tables) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureLeasesTables Leases (Tables) Tables http://www.mtem.com/20200630/taxonomy/role/DisclosureLeases 27 false false R28.htm 100270 - Disclosure - Stock-Based Compensation (Tables) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureStockBasedCompensationTables Stock-Based Compensation (Tables) Tables http://www.mtem.com/20200630/taxonomy/role/DisclosureStockBasedCompensation 28 false false R29.htm 100280 - Disclosure - Organization and Summary of Significant Accounting Policies - Additional Information (Detail) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureOrganizationAndSummaryOfSignificantAccountingPoliciesAdditionalInformationDetail Organization and Summary of Significant Accounting Policies - Additional Information (Detail) Details 29 false false R30.htm 100290 - Disclosure - Net Loss Per Common Share - Additional Information (Detail) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureNetLossPerCommonShareAdditionalInformationDetail Net Loss Per Common Share - Additional Information (Detail) Details 30 false false R31.htm 100300 - Disclosure - Research and Development Agreements - Schedule of Research and Development Revenues Disaggregated by Location (Detail) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureResearchAndDevelopmentAgreementsScheduleOfResearchAndDevelopmentRevenuesDisaggregatedByLocationDetail Research and Development Agreements - Schedule of Research and Development Revenues Disaggregated by Location (Detail) Details 31 false false R32.htm 100310 - Disclosure - Research and Development Agreements - Schedule of Research and Development Revenue from Related Party Relates to Revenue from Research and Development Agreements (Detail) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureResearchAndDevelopmentAgreementsScheduleOfResearchAndDevelopmentRevenueFromRelatedPartyRelatesToRevenueFromResearchAndDevelopmentAgreementsDetail Research and Development Agreements - Schedule of Research and Development Revenue from Related Party Relates to Revenue from Research and Development Agreements (Detail) Details 32 false false R33.htm 100320 - Disclosure - Research and Development Agreements - Schedule of Deferred Revenue, Other Liabilities for Co-share Payments and Accounts Receivable Balances from the Research and Development Agreements (Detail) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureResearchAndDevelopmentAgreementsScheduleOfDeferredRevenueOtherLiabilitiesForCoSharePaymentsAndAccountsReceivableBalancesFromResearchAndDevelopmentAgreementsDetail Research and Development Agreements - Schedule of Deferred Revenue, Other Liabilities for Co-share Payments and Accounts Receivable Balances from the Research and Development Agreements (Detail) Details 33 false false R34.htm 100330 - Disclosure - Research and Development Agreements - Additional Information (Detail) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureResearchAndDevelopmentAgreementsAdditionalInformationDetail Research and Development Agreements - Additional Information (Detail) Details 34 false false R35.htm 100340 - Disclosure - Marketable Securities and Fair Value Measurements - Financial Assets at Fair Value on Recurring Basis (Detail) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureMarketableSecuritiesAndFairValueMeasurementsFinancialAssetsAtFairValueOnRecurringBasisDetail Marketable Securities and Fair Value Measurements - Financial Assets at Fair Value on Recurring Basis (Detail) Details 35 false false R36.htm 100350 - Disclosure - Marketable Securities and Fair Value Measurements - Summary of Company's Available-for-Sale Securities (Detail) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureMarketableSecuritiesAndFairValueMeasurementsSummaryOfCompanySAvailableForSaleSecuritiesDetail Marketable Securities and Fair Value Measurements - Summary of Company's Available-for-Sale Securities (Detail) Details 36 false false R37.htm 100360 - Disclosure - Marketable Securities and Fair Value Measurements - Summary of Contractual Maturities of Available-for-Sale-Investment (Detail) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureMarketableSecuritiesAndFairValueMeasurementsSummaryOfContractualMaturitiesOfAvailableForSaleInvestmentDetail Marketable Securities and Fair Value Measurements - Summary of Contractual Maturities of Available-for-Sale-Investment (Detail) Details 37 false false R38.htm 100370 - Disclosure - Marketable Securities and Fair Value Measurements - Additional Information (Detail) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureMarketableSecuritiesAndFairValueMeasurementsAdditionalInformationDetail Marketable Securities and Fair Value Measurements - Additional Information (Detail) Details 38 false false R39.htm 100380 - Disclosure - Balance Sheet Components - Components of Accrued Liabilities (Detail) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureBalanceSheetComponentsComponentsOfAccruedLiabilitiesDetail Balance Sheet Components - Components of Accrued Liabilities (Detail) Details 39 false false R40.htm 100390 - Disclosure - Property and Equipment - Components of Property and Equipment (Detail) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosurePropertyAndEquipmentComponentsOfPropertyAndEquipmentDetail Property and Equipment - Components of Property and Equipment (Detail) Details 40 false false R41.htm 100400 - Disclosure - Property and Equipment - Additional Information (Detail) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosurePropertyAndEquipmentAdditionalInformationDetail Property and Equipment - Additional Information (Detail) Details 41 false false R42.htm 100410 - Disclosure - Borrowing Arrangements - Additional Information (Detail) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureBorrowingArrangementsAdditionalInformationDetail Borrowing Arrangements - Additional Information (Detail) Details 42 false false R43.htm 100420 - Disclosure - Borrowing Arrangements - Schedule of Required Future Principal Payments (Detail) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureBorrowingArrangementsScheduleOfRequiredFuturePrincipalPaymentsDetail Borrowing Arrangements - Schedule of Required Future Principal Payments (Detail) Details 43 false false R44.htm 100430 - Disclosure - Leases - Additional Information (Detail) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureLeasesAdditionalInformationDetail Leases - Additional Information (Detail) Details 44 false false R45.htm 100440 - Disclosure - Leases - Components of Lease Expense (Detail) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureLeasesComponentsOfLeaseExpenseDetail Leases - Components of Lease Expense (Detail) Details 45 false false R46.htm 100450 - Disclosure - Leases - Schedule of Balance Sheets Classification of Leases (Detail) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureLeasesScheduleOfBalanceSheetsClassificationOfLeasesDetail Leases - Schedule of Balance Sheets Classification of Leases (Detail) Details 46 false false R47.htm 100460 - Disclosure - Leases - Schedule of Leases Information (Detail) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureLeasesScheduleOfLeasesInformationDetail Leases - Schedule of Leases Information (Detail) Details 47 false false R48.htm 100470 - Disclosure - Leases - Schedule of Maturities of Lease Liabilities (Detail) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureLeasesScheduleOfMaturitiesOfLeaseLiabilitiesDetail Leases - Schedule of Maturities of Lease Liabilities (Detail) Details 48 false false R49.htm 100490 - Disclosure - Leases - Supplemental Cash Flow Information (Detail) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureLeasesSupplementalCashFlowInformationDetail Leases - Supplemental Cash Flow Information (Detail) Details 49 false false R50.htm 100500 - Disclosure - Contractual Commitments - Additional Information (Detail) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureContractualCommitmentsAdditionalInformationDetail Contractual Commitments - Additional Information (Detail) Details 50 false false R51.htm 100510 - Disclosure - Stock-Based Compensation - Stock-Based Compensation Expense (Detail) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureStockBasedCompensationStockBasedCompensationExpenseDetail Stock-Based Compensation - Stock-Based Compensation Expense (Detail) Details 51 false false R52.htm 100520 - Disclosure - Stock-Based Compensation - Additional Information (Detail) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureStockBasedCompensationAdditionalInformationDetail Stock-Based Compensation - Additional Information (Detail) Details 52 false false R53.htm 100530 - Disclosure - Stock-Based Compensation - Weighted-Average Fair Value Valuation Assumptions (Detail) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureStockBasedCompensationWeightedAverageFairValueValuationAssumptionsDetail Stock-Based Compensation - Weighted-Average Fair Value Valuation Assumptions (Detail) Details 53 false false R54.htm 100540 - Disclosure - Stock-Based Compensation - Stock Option Activity Under Equity Incentive Plan (Detail) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureStockBasedCompensationStockOptionActivityUnderEquityIncentivePlanDetail Stock-Based Compensation - Stock Option Activity Under Equity Incentive Plan (Detail) Details 54 false false R55.htm 100550 - Disclosure - In-Process Research and Development - Additional Information (Detail) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureInProcessResearchAndDevelopmentAdditionalInformationDetail In-Process Research and Development - Additional Information (Detail) Details 55 false false R56.htm 100560 - Disclosure - Subsequent Events - Additional Information (Detail) Sheet http://www.mtem.com/20200630/taxonomy/role/DisclosureSubsequentEventsAdditionalInformationDetail Subsequent Events - Additional Information (Detail) Details 56 false false All Reports Book All Reports mtem-10q_20200630.htm mtem-20200630.xsd mtem-20200630_cal.xml mtem-20200630_def.xml mtem-20200630_lab.xml mtem-20200630_pre.xml mtem-ex103_362.htm mtem-ex311_7.htm mtem-ex312_6.htm mtem-ex321_8.htm http://xbrl.sec.gov/country/2020-01-31 http://fasb.org/us-gaap/2020-01-31 http://xbrl.sec.gov/dei/2019-01-31 http://fasb.org/srt/2020-01-31 http://xbrl.sec.gov/stpr/2018-01-31 true true