S-1 Files S-1: RSU & Capital Gains Tax Exposure Calculator — Jul 29, 2026

What Changed

Moleculin Biotech filed an S-1 registration statement on July 29, 2026, initiating the public offering process for a biotech company with no confirmed revenue model yet disclosed. The filing size of 1 MB suggests a standard IPO structure, likely targeting a raise between $50M and $150M based on typical biotech S-1 patterns. For employees holding pre-IPO equity, this triggers a 180-day lockup period and converts paper grants into taxable events within 12 to 18 months.

The Numbers That Matter

Equity Component	Pre-IPO Value	Post-IPO Tax Exposure	Net Proceeds (35% Tax Bracket)
10,000 ISOs at $2 strike	$20,000 exercise cost	AMT on $80,000 spread	$32,000 after-tax gain
25,000 RSUs (unvested)	$0 current tax	Ordinary income on $250,000	$162,500 net cash
Early exercised shares	$15,000 sunk cost	Long-term cap gains on $185,000	$157,750 after 20% rate
Cash bonus (pre-IPO retention)	$50,000 gross	$32,500 net (35% marginal)	Immediate liquidity

What This Means for Your Portfolio

If you hold 25,000 RSUs vesting over four years and the IPO prices at $10 per share, your gross position is worth $250,000 on day one. Ordinary income tax at 35% federal plus 10% state reduces net proceeds to $137,500 after withholding. The lockup period delays liquidity for six months, during which the stock could move 40% to 60% in either direction based on 2025 biotech IPO volatility data.

Scenario Analysis

Portfolio Allocation	Equity Value at IPO	Tax Liability (45% Blended)	Net After-Tax Proceeds	Downside if Stock Drops 50% Post-Lockup
$500K pre-IPO equity	$500,000	$225,000	$275,000	$137,500 net remaining
$1M pre-IPO equity	$1,000,000	$450,000	$550,000	$275,000 net remaining
$2M pre-IPO equity	$2,000,000	$900,000	$1,100,000	$550,000 net remaining

The $500K position assumes 50,000 shares at a $10 IPO price. The $1M and $2M positions scale linearly. All figures net of 35% federal income tax, 10% state tax, and 0% NIIT (below the $200K threshold for single filers). Downside scenario applies a 50% post-lockup decline. Biotech stocks have historically experienced significant volatility in the period following lockup expiration.

What Happens Next

The S-1 filing enters a 30 to 90-day SEC review period. Moleculin will amend the filing at least twice before pricing. Employees with ISOs face a decision about timing and strategy. The decision between exercising before or after an IPO involves multiple factors including current tax situation, expected stock price, and personal financial circumstances. Early exercise on 10,000 ISOs at a $2 strike costs $20,000 today but could result in tax benefits if the stock prices at $10 and you hold past one year, though this depends on individual tax circumstances. The AMT credit may recover in year two if your regular tax exceeds AMT in that period.

For RSU holders, the tax bill arrives whether you sell or not. If 6,250 shares vest in quarter one post-IPO at $10, you owe $21,875 in taxes even if you hold the stock. Most employees sell 40% to 50% of vested shares immediately to cover withholding. The remaining position becomes a concentrated equity bet. If Moleculin represents more than 15% of your net worth post-IPO, you are carrying single-stock risk that most wealth managers would flag for reduction.

The lockup expires 180 days after pricing. Institutional investors and employees can sell starting on day 181. Biotech stocks have historically experienced notable volatility in the period following lockup expiration. If you plan to liquidate, your execution window is narrow. Waiting past day 190 increases the risk of selling into a post-lockup selloff already underway.

Frequently Asked Questions

Q: How much of my RSU tax liability can I defer? A: Zero. RSUs are taxed as ordinary income on the vesting date at fair market value, regardless of whether you sell.

Q: What factors should I consider regarding ISO exercise timing? A: The decision between exercising ISOs before or after an IPO involves weighing AMT implications, anticipated stock price movements, and your personal tax situation. Consider consulting a tax advisor for guidance specific to your circumstances.

Q: What percentage of my net worth should I keep in a single IPO stock post-lockup? A: Most institutional advisors recommend reducing concentrated positions to under 10% of net worth within 12 months of liquidity.

Q: Can I sell shares during the lockup period? A: No. The 180-day lockup applies to all employees, founders, and early investors unless the underwriter grants an early release, which happens in fewer than 5% of biotech IPOs.

Run the Numbers

Use CalcMoney's Calculate Your After-Tax RSU Proceeds to model your exact tax liability across federal, state, and NIIT thresholds before the lockup expires.

Important Disclosure

This article is for informational purposes only and does not constitute professional financial advice. The tax and financial scenarios presented depend on individual circumstances, current tax law, and personal investment objectives. Consult a qualified tax advisor, financial advisor, or attorney before making any financial or investment decisions related to IPO equity or equity compensation.

Run the Numbers: Capital Gains Tax Terminal on CalcMoney — see your exact figures under current market conditions.

Data sourced from SEC EDGAR S-1 Filings (IPO). Rates and thresholds are for informational purposes only. Consult a licensed financial advisor before making mortgage, investment, or tax decisions.

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