March 2019

PRELIMINARY PRICING SUPPLEMENT Dated March 6, 2019

Filed Pursuant to Rule 424(b)(2)

Registration Statement No. 333-225551

(To Prospectus dated October 31, 2018 and Product Supplement dated October 31, 2018)

$10 per Buffered PLUS and integral multiples thereof

▪    If the underlying return is positive:
The lesser of (a) $10 + Leveraged Upside Payment and (b) Maximum Payment at Maturity

▪    If the underlying return is zero or negative and the percentage decline from the initial price to the final price is equal to or less than the buffer amount:
Stated Principal Amount of $10

▪   If the underlying return is negative and the percentage decline from the initial price to the final price is greater than the buffer amount:
$10 + [$10 x (Underlying Return + Buffer Amount)]
Under these circumstances, you will lose a percentage of your stated principal amount equal to the percentage decline of the underlying fund from the initial price to the final price in excess of the buffer amount, and in extreme situations, you could lose almost all of your initial investment.

(Final price - Initial price) / Initial price

10%

   2.00%^(a)

+ 0.50%^(b)

2.50%

Approximately 24 months

You believe that the percentage decline of the underlying fund from the initial price to the final price will be greater than the buffer amount or you cannot tolerate receiving a payment at maturity that may be less than the stated principal amount and as low as the minimum payment amount.

§      If the underlying return is positive:
The lesser of (a) $10 + Leveraged Upside Payment and (b) Maximum Payment at Maturity
In no event will the payment at maturity exceed the maximum payment at maturity.

§      If the underlying return is zero or negative and the percentage decline from the initial price to the final price is equal to or less than the buffer amount::
Stated Principal Amount of $10

§      If the underlying return is negative and the percentage decline from the initial price to the final price is greater than the buffer amount:
$10 + [$10 x (Underlying Return + Buffer Amount)]
Under these circumstances, you will lose a percentage of your stated principal amount equal to the percentage decline of the underlying fund from the initial price to the final price in excess of the buffer amount, and in extreme situations, you could lose almost all of your initial investment.

The quotient, expressed as a percentage, of (i) the final price of the underlying fund minus the initial price of the underlying fund, divided by (ii) the initial price of the underlying fund. Expressed as a formula:

(Final price - Initial price) / Initial price

US90281C4353

The U.S. federal income tax consequences of your investment in the Buffered PLUS are uncertain. There are no statutory provisions, regulations, published rulings or judicial decisions addressing the characterization for U.S. federal income tax purposes of securities with terms that are substantially the same as the Buffered PLUS. Some of these tax consequences are summarized below, but we urge you to read the more detailed discussion in “Material U.S. Federal Income Tax Consequences” , including the section “— Securities Treated as Prepaid Derivatives or Prepaid Forwards” in the accompanying product supplement and to discuss the tax consequences of your particular situation with your tax advisor. This discussion is based upon the Internal Revenue Code of 1986, as amended (the “Code”), final, temporary and proposed U.S. Treasury Department (the “Treasury”) regulations, rulings and decisions, in each case, as available and in effect as of the date hereof, all of which are subject to change, possibly with retroactive effect. Tax consequences under state, local and non-U.S. laws are not addressed herein. No ruling from the U.S. Internal Revenue Service (the “IRS”) has been sought as to the U.S. federal income tax consequences of your investment in the Buffered PLUS, and the following discussion is not binding on the IRS.

U.S. Tax Treatment. Pursuant to the terms of the Buffered PLUS, UBS and you agree, in the absence of a statutory or regulatory change or an administrative determination or judicial ruling to the contrary, to characterize the Buffered PLUS as prepaid derivative contracts with respect to the underlying equity. If your Buffered PLUS are so treated, subject to the discussion below regarding Section 1260 of the Code, you should generally recognize gain or loss upon the taxable disposition of your Buffered PLUS. Such gain or loss should generally be long-term capital gain or loss if you hold your Buffered PLUS for more than one year (otherwise such gain or loss would be short-term capital gain or loss if held for one year or less) in an amount equal to the difference between the amount you receive at such time and the amount you paid for your Buffered PLUS.

Section 1260. Because the Buffered PLUS are linked to the shares of an ETF, there is a risk that an investment in the Buffered PLUS could be treated as a “constructive ownership transaction” within the meaning of Section 1260 of the Code. A “constructive ownership transaction” includes a contract under which an investor will receive payment equal to or credit for the future value of any equity interest in certain “passthru entities” (including regulated investment companies such as ETFs, real estate investment trusts and passive foreign investment companies). Under the “constructive ownership” rules, if an investment in the Buffered PLUS is treated as a “constructive ownership transaction,” any long-term capital gain recognized by a U.S. holder (as defined under “Material U.S. Federal Income Tax Consequences” in the accompanying product supplement) in respect of the Buffered PLUS would be recharacterized as ordinary income to the extent such gain exceeds the amount of “net underlying long-term capital gain”(as defined in Section 1260 of the Code) of the U.S. holder (the “Excess Gain”). In addition, an interest charge would also apply to any deemed underpayment of tax in respect of any Excess Gain to the extent such gain would have resulted in gross income inclusion for the U.S. holder in taxable years prior to the taxable year of the taxable disposition of the Buffered PLUS (assuming such income accrued such that the amount in each successive year is equal to the income in the prior year increased at a constant rate equal to the applicable federal rate as of the date of taxable disposition of the Buffered PLUS).

It is not clear to what extent any long-term capital gain recognized by a U.S.

holder in respect of the Buffered PLUS would be recharacterized as ordinary income and subject to the interest charge described above, in part, because it is not clear how the “net underlying long-term capital gain” would be computed in respect of the Buffered PLUS. Under Section 1260 of the Code, the net underlying long-term capital gain is generally the net long-term capital gain a taxpayer would have recognized by investing in the underlying “passthru entity” at the inception of the constructive ownership transaction and selling on the date the constructive ownership transaction is closed out (i.e. at maturity or earlier disposition). It is possible that because the U.S. holder does not share in distributions made on the underlying fund, these distributions could be excluded from the calculation of the amount and character of gain, if any, that would have been realized had the U.S. holder held the underlying fund directly and that the application of constructive ownership rules may not recharacterize adversely a significant portion of the long-term capital gain you may recognize with respect to the Buffered PLUS. However, it is also possible that all or a portion of your gain with respect to the Buffered PLUS could be treated as “Excess Gain” because the underlying fund is an ETF, the “net underlying long-term capital gain” could equal the amount of long-term capital gain a U.S. holder would have recognized if on the issue date of the Buffered PLUS the holder had invested, pro rata, the principal amount of the Buffered PLUS in shares of the underlying fund and sold those shares for their fair market value on the date the Buffered PLUS are sold, exchanged or retired. In addition, all or a portion of your gain recognized with respect to the Buffered PLUS could be “Excess Gain” if you purchase the Buffered PLUS for an amount that is less than the principal amount of the Buffered PLUS or if the return on the Buffered PLUS is adjusted to take into account any extraordinary dividends that are paid on the shares of the underlying fund. Furthermore, unless otherwise established by clear and convincing evidence, the “net underlying long-term capital gain” is treated as zero. Accordingly, it is possible that all or a portion of any gain on the taxable disposition of the Buffered PLUS after one year could be treated as “Excess Gain” from a “constructive ownership transaction,” which gain would be recharacterized as ordinary income, and subject to an interest charge. Because the application of the constructive ownership rules to the Buffered PLUS is unclear, you are urged to consult your tax advisor regarding the potential application of the “constructive ownership” rules to an investment in the Buffered PLUS.

Based on certain factual representations received from us, our counsel, Cadwalader, Wickersham & Taft LLP, is of the opinion that it would be reasonable to treat your Buffered PLUS in the manner described above. However, because there is no authority that specifically addresses the tax treatment of the Buffered PLUS, it is possible that your Buffered PLUS could alternatively be treated for tax purposes as a single contingent payment debt instrument, or pursuant to some other characterization (including possible treatment as a “constructive ownership transaction”), such that the timing and character of your income from the Buffered PLUS could differ materially and adversely from the treatment described above, as described further under “Material U.S. Federal Income Tax Consequences”, including the section “— Securities Treated as Prepaid Derivatives or Prepaid Forwards”, in the accompanying product supplement.

Notice 2008-2. In 2007, the IRS released a notice that may affect the taxation of holders of the Buffered PLUS. According to Notice 2008-2, the IRS and the Treasury are actively considering whether the holder of an instrument similar to the Buffered PLUS should be required to accrue ordinary income on a current basis, and they are seeking taxpayer comments on the subject. It is not possible to determine what guidance they will ultimately issue, if any. It is possible, however, that under such guidance, holders of the Buffered PLUS will ultimately be required to accrue income currently and this could be applied on a retroactive basis. The IRS and the Treasury are also considering other relevant issues, including whether additional gain or loss from such instruments should be treated as ordinary or capital, whether non-U.S. holders of such instruments should be subject to withholding tax on any deemed income accruals and whether the special ‘‘constructive ownership rules’’ of Section 1260 of the Code should be applied to such instruments. Both U.S. and non-U.S. holders are urged to consult their tax advisors concerning the

significance, and the potential impact, of the above considerations.

Medicare Tax on Net Investment Income. U.S. holders that are individuals, estates, and certain trusts are subject to an additional 3.8% tax on all or a portion of their ”net investment income”, which may include any income or gain realized with respect to the Buffered PLUS, to the extent of their net investment income that when added to their other modified adjusted gross income, exceeds $200,000 for an unmarried individual, $250,000 for a married taxpayer filing a joint return (or a surviving spouse), $125,000 for a married individual filing a separate return or the amount at which the highest tax bracket begins for an estate or trust. The 3.8% Medicare tax is determined in a different manner than the income tax. You should consult your tax advisor as to the consequences of the 3.8% Medicare tax.

Specified Foreign Financial Assets. Certain U.S. holders that own “specified foreign financial assets” in excess of an applicable threshold may be subject to reporting obligations with respect to such assets with their tax returns, especially if such assets are held outside the custody of a U.S. financial institution. You are urged to consult your tax advisor as to the application of this legislation to your ownership of the Buffered PLUS.

Non-U.S. Holders. Subject to Section 871(m) of the Code and FATCA (as discussed below), if you are not a U.S. holder, you should generally not be subject to U.S. withholding tax with respect to payments on your Buffered PLUS and you should not be subject to generally applicable information reporting and backup withholding requirements with respect to payments on your Buffered PLUS if you comply with certain certification and identification requirements, including providing us (and/or the applicable withholding agent) with a validly executed and fully completed applicable IRS Form W-8. Subject Section 871(m) of the Code, discussed below, gain from the taxable disposition of a Buffered PLUS generally should not be subject to U.S. tax unless (i) such gain is effectively connected with a trade or business conducted by the non-U.S. holder in the U.S., (ii) the non-U.S. holder is a non-resident alien individual and is present in the U.S. for 183 days or more during the taxable year of such taxable disposition and certain other conditions are satisfied or (iii) the non-U.S. holder has certain other present or former connections with the U.S.

Section 871(m). A 30% withholding tax (which may be reduced by an applicable income tax treaty) is imposed under Section 871(m) of the Code on certain “dividend equivalents” paid or deemed paid to a non-U.S. holder with respect to a “specified equity-linked instrument” that references one or more dividend-paying U.S. equity securities or indices containing U.S. equity securities. The withholding tax can apply even if the instrument does not provide for payments that reference dividends. Treasury regulations provide that the withholding tax applies to all dividend equivalents paid or deemed paid on specified equity-linked instruments that have a delta of one (“delta-one specified equity-linked instruments”) issued after 2016 and to all dividend equivalents paid or deemed paid on all other specified equity-linked instruments issued after 2018. However, the IRS has issued guidance that states that the Treasury and the IRS intend to amend the effective dates of the Treasury regulations to provide that withholding on dividend equivalents paid or deemed paid will not apply to specified equity-linked instruments that are not delta-one specified equity-linked instruments and are issued before January 1, 2021.

Based on our determination that the Buffered PLUS are not “delta-one” with respect to any underlying equity or any U.S. index constituent stock, our counsel is of the opinion that the Buffered PLUS should not be delta-one specified equity-linked instruments and thus should not be subject to withholding on dividend equivalents. Our determination is not binding on the IRS, and the IRS may disagree with this determination. Furthermore, the application of Section 871(m) of the Code will depend on our determinations made upon issuance of the Buffered PLUS. If withholding is required, we will not make payments of any additional amounts.

Nevertheless, after issuance, it is possible that your Buffered PLUS could be

deemed to be reissued for tax purposes upon the occurrence of certain events affecting the underlying equity, underlying equity constituents or your Buffered PLUS, and following such occurrence your Buffered PLUS could be treated as delta-one specified equity-linked instruments that are subject to withholding on dividend equivalents. It is also possible that withholding tax or other tax under Section 871(m) of the Code could apply to the Buffered PLUS under these rules if you enter, or have entered, into certain other transactions in respect of the underlying equity, underlying equity constituents or the Buffered PLUS. If you enter, or have entered, into other transactions in respect of the underlying equity, underlying equity constituents or the Buffered PLUS, you should consult your tax advisor regarding the application of Section 871(m) of the Code to your Buffered PLUS in the context of your other transactions.

Because of the uncertainty regarding the application of the 30% withholding tax on dividend equivalents to the Buffered PLUS, you are urged to consult your tax advisor regarding the potential application of Section 871(m) of the Code and the 30% withholding tax to an investment in the Buffered PLUS.

Foreign Account Tax Compliance Act. The Foreign Account Tax Compliance Act (“FATCA”) was enacted on March 18, 2010, and imposes a 30% U.S. withholding tax on “withholdable payments” (i.e., certain U.S.-source payments, including interest (and original issue discount), dividends, other fixed or determinable annual or periodical gain, profits, and income, and on the gross proceeds from a disposition of property of a type which can produce U.S.-source interest or dividends) and “passthru payments” (i.e., certain payments attributable to withholdable payments) made to certain foreign financial institutions (and certain of their affiliates) unless the payee foreign financial institution agrees (or is required), among other things, to disclose the identity of any U.S. individual with an account of the institution (or the relevant affiliate) and to annually report certain information about such account. FATCA also requires withholding agents making withholdable payments to certain foreign entities that do not disclose the name, address, and taxpayer identification number of any substantial U.S. owners (or do not certify that they do not have any substantial U.S. owners) to withhold tax at a rate of 30%. Under certain circumstances, a holder may be eligible for refunds or credits of such taxes.

Pursuant to final and temporary Treasury regulations and other IRS guidance, the withholding and reporting requirements under FATCA will generally apply to certain “withholdable payments”, will not apply to gross proceeds on a sale or disposition, and will apply to certain foreign passthru payments only to the extent that such payments are made after the date that is two years after final regulations defining the term “foreign passthru payment” are published. If withholding is required, we (or the applicable paying agent) will not be required to pay additional amounts with respect to the amounts so withheld. Foreign financial institutions and non-financial foreign entities located in jurisdictions that have an intergovernmental agreement with the U.S. governing FATCA may be subject to different rules.

Investors should consult their tax advisors about the application of FATCA, in particular if they may be classified as financial institutions (or if they hold their Buffered PLUS through a foreign entity) under the FATCA rules.

Proposed Legislation. In 2007, legislation was introduced in Congress that, if it had been enacted, would have required holders of securities similar to the Buffered PLUS purchased after the bill was enacted to accrue interest income over the term of such securities despite the fact that there will be no interest payments over the term of such securities.

Furthermore, in 2013, the House Ways and Means Committee released in draft form certain proposed legislation relating to financial instruments. If it had been enacted, the effect of this legislation generally would have been to require instruments such as the Buffered PLUS to be marked to market on an annual basis with all gains and losses to be treated as ordinary, subject to certain exceptions.

It is not possible to predict whether any similar or identical bills will be enacted

in the future, or whether any such bill would affect the tax treatment of your Buffered PLUS. You are urged to consult your tax advisor regarding the possible changes in law and their possible impact on the tax treatment of your Buffered PLUS.

Both U.S. and non-U.S. holders are urged to consult their tax advisors concerning the application of U.S. federal income tax laws to their particular situations, as well as any tax consequences of the purchase, beneficial ownership and disposition of the Buffered PLUS arising under the laws of any state, local, non-U.S. or other taxing jurisdiction (including the taxing jurisdictions of the underlying equity constituent issuers).

We will use the net proceeds we receive from the sale of the Buffered PLUS for the purposes we describe in the accompanying prospectus under “Use of Proceeds and Hedging.” We and/or our affiliates may also use those proceeds in transactions intended to hedge our obligations under the Buffered PLUS as described below.

In connection with the sale of the Buffered PLUS, we and/or our affiliates may enter into hedging transactions involving the execution of swaps, futures and/or option transactions on the underlying fund or underlying constituents, or purchases and sales of Buffered PLUS, in each case before, on and/or after the pricing date of the Buffered PLUS. From time to time, we and/or our affiliates may enter into additional hedging transactions or unwind those we have entered into.

We and/or our affiliates may acquire a long or short position in securities similar to the Buffered PLUS from time to time and may, in our or their sole discretion, hold or resell those securities.

The hedging activity discussed above may adversely affect the market value of the Buffered PLUS from time to time and payment on the Buffered PLUS at maturity. See “Risk Factors” herein for a discussion of these adverse effects.

Pursuant to the terms of a distribution agreement, UBS will agree to sell to UBS Securities LLC, and UBS Securities LLC will agree to purchase from UBS, the stated principal amount of the Buffered PLUS specified on the front cover of this document at the price to public less a fee of $0.25 per $10.00 stated principal amount of Buffered PLUS. UBS Securities LLC will agree to resell all of the Buffered PLUS to Morgan Stanley Smith Barney (also known as “Morgan Stanley Wealth Management”) with an underwriting discount of $0.25 reflecting a fixed structuring fee of $0.05 and a fixed sales commission of $0.20 per $10.00 stated principal amount of Buffered PLUS that Morgan Stanley Wealth Management sells.

UBS, UBS Securities LLC or any other affiliate of UBS may use this document, the accompanying product supplement and the accompanying prospectus in a market-making transaction for any Buffered PLUS after their initial sale. In connection with this offering, UBS, UBS Securities LLC, any other affiliate of UBS or any other securities dealers may distribute this document, the accompanying product supplement and the accompanying prospectus electronically. Unless UBS or its agent informs the purchaser otherwise in the confirmation of sale, this document, the accompanying product supplement and the accompanying prospectus are being used in a market-making transaction.

Conflicts of Interest — UBS Securities LLC is an affiliate of UBS and, as such, has a “conflict of interest” in this offering within the meaning of Financial Industry Regulatory Authority, Inc. (“FINRA”) Rule 5121. In addition, UBS will receive the net proceeds (excluding the underwriting discount) from the initial public offering of the Buffered PLUS, thus creating an additional conflict of interest within the meaning of FINRA Rule 5121. UBS Securities LLC is not permitted to sell Buffered PLUS in this offering to an account over which it exercises discretionary authority without the prior specific written approval of the account holder.

UBS Securities LLC and its affiliates may offer to buy or sell the Buffered PLUS in the secondary market (if any) at prices greater than UBS’ internal valuation — The value of the Buffered PLUS at any time will vary based on many factors that cannot be predicted. However, the price (not including UBS Securities LLC’s or any affiliate’s customary bid-ask spreads) at which UBS Securities LLC or any affiliate would offer to buy or sell the Buffered PLUS immediately after the pricing date in the secondary market is expected to exceed the estimated initial value of the Buffered PLUS as determined by reference to our internal pricing models. The amount of the excess will decline to zero on a straight line basis over a period ending no later than 6 weeks after the pricing date, provided that UBS Securities LLC may shorten the period based on various factors, including the magnitude of purchases and other negotiated provisions with selling agents. Notwithstanding the foregoing, UBS Securities LLC and its affiliates are not required to make a market for the Buffered PLUS and may stop making a market at any time. For more information about secondary market offers and the estimated initial value of the Buffered PLUS, see “Risk Factors — Fair value considerations” and “— Limited or no secondary market and secondary market price considerations” herein.

= $10.00 + lesser of (a) ($10.00 x 2.0 x 10%) and (b) ($10.00 x 22.00%)

= lesser of (a) $12.00 and (b) $12.20