0000778207 2025-12-31 2025-12-31 0000778207 tst:S000007902Member 2025-12-31 2025-12-31 false 2025-12-31 497 0000778207 2026-05-01 N-1A <div style="margin-top:0pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;font-weight:bold;text-align:center;">TRANSAMERICA SERIES TRUST </div><div style="margin-top:12pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;font-weight:bold;text-align:center;">Supplement to the Currently Effective Prospectus, Summary Prospectus and Statement of Additional Information </div><div style="margin-top:6pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;font-weight:bold;text-align:center;">Transamerica JPMorgan Enhanced Index VP (the “portfolio”) </div><div style="margin-top:6pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;font-weight:bold;text-align:center;">* * * </div><div style="margin-top:6pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;text-align:justify;">At a special meeting held on October 7, 2026, the portfolio’s investors approved a change in the portfolio’s classification from a diversified company to a non‑diversified company. </div><div style="margin-top:6pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;text-align:justify;">Effective on or about November 1, 2026, the following information will supplement and supersede any contrary information contained in the Prospectus, Summary Prospectus and Statement of Additional Information, as applicable, concerning the portfolio. </div><div style="margin-top:6pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;font-weight:bold;text-align:center;">* * * </div><div style="margin-top:6pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;font-weight:bold;">PRINCIPAL INVESTMENT STRATEGIES: </div><div style="margin-top:6pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;"><span style="font-style:italic">The following will be added as the last sentence in the portfolio’s “Principal Investment Strategies” section in the Prospectus and Summary Prospectus, and as the seventh paragraph of the “More on Each Portfolio’s Strategies and Investments” section in the Prospectus concerning the portfolio: </span></div><div style="margin-top:6pt;margin-bottom:0pt;margin-left:4%;font-size:10pt;font-family:times new roman;text-align:justify;">The portfolio is non‑diversified. </div><div style="margin-top:6pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;font-weight:bold;text-align:center;">* * * </div><div style="margin-top:6pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;font-weight:bold;">PRINCIPAL RISKS: </div><div style="margin-top:6pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;"><span style="font-style:italic">The following risk will be added as a key risk following the “Value Investing” risk in the “Principal Risks” section of the Prospectus and the Summary Prospectus for the portfolio: </span></div><div style="margin-top:6pt;margin-bottom:0pt;margin-left:4%;font-size:10pt;font-family:times new roman;text-align:justify;"><span style="font-weight:bold">Non‑Diversification</span> – As a non‑diversified portfolio, the portfolio may invest a larger percentage of its assets in a smaller number of issuers than a diversified fund. Investing in a smaller number of issuers will make the portfolio more susceptible to the risks associated with investing in those issuers. </div><div style="margin-top:6pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;font-weight:bold;text-align:center;">* * * </div><div style="margin-top:120pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;font-weight:bold;text-align:center;">Investors Should Retain this Supplement for Future Reference </div><div style="margin-top:6pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;font-weight:bold;">October 22, 2026 </div> <div style="margin-top:0pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;font-weight:bold;text-align:center;">TRANSAMERICA SERIES TRUST </div><div style="margin-top:12pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;font-weight:bold;text-align:center;">Supplement to the Currently Effective Prospectus, Summary Prospectus and Statement of Additional Information </div><div style="margin-top:6pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;font-weight:bold;text-align:center;">Transamerica JPMorgan Enhanced Index VP (the “portfolio”) </div><div style="margin-top:6pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;font-weight:bold;text-align:center;">* * * </div><div style="margin-top:6pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;text-align:justify;">At a special meeting held on October 7, 2026, the portfolio’s investors approved a change in the portfolio’s classification from a diversified company to a non‑diversified company. </div><div style="margin-top:6pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;text-align:justify;">Effective on or about November 1, 2026, the following information will supplement and supersede any contrary information contained in the Prospectus, Summary Prospectus and Statement of Additional Information, as applicable, concerning the portfolio. </div><div style="margin-top:6pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;font-weight:bold;text-align:center;">* * * </div><div style="margin-top:6pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;font-weight:bold;">PRINCIPAL INVESTMENT STRATEGIES: </div><div style="margin-top:6pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;"><span style="font-style:italic">The following will be added as the last sentence in the portfolio’s “Principal Investment Strategies” section in the Prospectus and Summary Prospectus, and as the seventh paragraph of the “More on Each Portfolio’s Strategies and Investments” section in the Prospectus concerning the portfolio: </span></div><div style="margin-top:6pt;margin-bottom:0pt;margin-left:4%;font-size:10pt;font-family:times new roman;text-align:justify;">The portfolio is non‑diversified. </div><div style="margin-top:6pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;font-weight:bold;text-align:center;">* * * </div><div style="margin-top:6pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;font-weight:bold;">PRINCIPAL RISKS: </div><div style="margin-top:6pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;"><span style="font-style:italic">The following risk will be added as a key risk following the “Value Investing” risk in the “Principal Risks” section of the Prospectus and the Summary Prospectus for the portfolio: </span></div><div style="margin-top:6pt;margin-bottom:0pt;margin-left:4%;font-size:10pt;font-family:times new roman;text-align:justify;"><span style="font-weight:bold">Non‑Diversification</span> – As a non‑diversified portfolio, the portfolio may invest a larger percentage of its assets in a smaller number of issuers than a diversified fund. Investing in a smaller number of issuers will make the portfolio more susceptible to the risks associated with investing in those issuers. </div><div style="margin-top:6pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;font-weight:bold;text-align:center;">* * * </div><div style="margin-top:120pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;font-weight:bold;text-align:center;">Investors Should Retain this Supplement for Future Reference </div><div style="margin-top:6pt;margin-bottom:0pt;font-size:10pt;font-family:times new roman;font-weight:bold;">October 22, 2026 </div> TRANSAMERICA SERIES TRUST