CSTL Strangle Strategy
CSTL (Castle Biosciences, Inc.), in the Healthcare sector, (Medical - Diagnostics & Research industry), listed on NASDAQ.
Castle Biosciences, Inc. functions as a commercial-stage diagnostics firm, with its primary objective being the provision of both diagnostic and prognostic testing services, specifically targeting various dermatological cancers. Their flagship product, DecisionDx-Melanoma, represents an advanced multi-gene expression profile (GEP) assay engineered to assess the probability of metastasis in patients afflicted with invasive cutaneous melanoma. In addition to their leading solution, the company has created several other specialized, proprietary tests. Among these is DecisionDx-UM, a GEP test tailored to forecast the risk of metastasis for individuals with uveal melanoma, a less common malignancy of the eye. Another key offering is DecisionDx-SCC, a distinctive 40-gene expression profile test that utilizes a patient's unique tumor biology to predict their specific risk of squamous cell carcinoma metastasis, particularly for those presenting with recognized risk factors. Moreover, they offer DecisionDx DiffDx-Melanoma and myPath Melanoma, both proprietary GEP tests employed to assist in the accurate diagnosis of ambiguous pigmented lesions.
CSTL (Castle Biosciences, Inc.) trades in the Healthcare sector, specifically Medical - Diagnostics & Research, with a market capitalization of approximately $737.0M, a beta of 1.02 versus the broader market, a 52-week range of 14.59-44.28, average daily share volume of 400K, a public-listing history dating back to 2019, approximately 784 full-time employees. These structural characteristics shape how CSTL stock options price implied volatility around earnings windows, capital events, and macro-driven sector rotations.
A beta of 1.02 places CSTL roughly in line with broader market moves, so the strategy payoff and realized volatility track the index-equivalent baseline.
What is a strangle on CSTL?
A long strangle buys an OTM call and an OTM put at offset strikes, cheaper than a straddle but requiring a larger underlying move to profit since both wings start out-of-the-money.
Current CSTL snapshot
As of June 30, 2026, spot at $23.83, ATM IV 30.60%, IV rank 6.40%, expected move 8.77%. The strangle on CSTL below is built from the same end-of-day chain, with strikes snapped to listed contracts and premiums pulled from the bid/ask midpoint at a 17-day expiry.
Why this strangle structure on CSTL specifically: CSTL IV at 30.60% is on the cheap side of its 1-year range, which favors premium-buying structures like a CSTL strangle, with a market-implied 1-standard-deviation move of approximately 8.77% (roughly $2.09 on the underlying). The 17-day window matched to the front-month expiry keeps theta exposure bounded while still capturing the post-snapshot move; longer-dated CSTL expiries trade a higher absolute premium for lower per-day decay. Position sizing on CSTL should anchor to the underlying notional of $23.83 per share and to the trader's directional view on CSTL stock.
CSTL strangle setup
The CSTL strangle below is built from the end-of-day chain, with each option leg priced at the bid/ask midpoint of its listed strike. With CSTL near $23.83, the first option leg uses a $25.02 strike; additional legs (when the strategy has them) anchor to spot-relative offsets. Premiums come from the bid/ask midpoint on the listed CSTL chain at a 17-day expiry; the cross-strike IV skew is reflected directly in the per-leg values rather than approximated. Quantity sizing assumes one contract per option leg (or 100 CSTL shares for the stock leg in covered calls and collars).
| Action | Type | Strike / Basis | Premium (est) |
|---|---|---|---|
| Buy 1 | Call | $25.02 | N/A |
| Buy 1 | Put | $22.64 | N/A |
CSTL strangle risk and reward
- Net Premium / Debit
- N/A
- Max Profit (per contract)
- Unbounded
- Max Loss (per contract)
- Unbounded
- Breakeven(s)
- None on modeled curve
- Risk / Reward Ratio
- N/A
Upside max profit is unbounded; downside max profit is bounded at the put strike minus the combined debit (reached at zero). Max loss equals the combined debit times 100 (reached anywhere between the two OTM strikes). Two breakevens at call-strike plus debit and put-strike minus debit.
CSTL strangle payoff curve
Modeled P&L at expiration across a range of underlying prices for the strangle on CSTL. Each row is one sampled price point from the computed payoff curve; the full curve uses 200 price points internally before being summarized into 10 rows here.
When traders use strangle on CSTL
Strangles on CSTL are the cheaper cousin of the straddle - traders use them when they want a large directional move but are willing to give up the inner-strike sensitivity in exchange for a lower up-front debit on the CSTL chain.
CSTL thesis for this strangle
The market-implied 1-standard-deviation range for CSTL extends from approximately $21.74 on the downside to $25.92 on the upside. A CSTL long strangle is the OTM cousin of the straddle: lower up-front cost but the underlying has to travel further past either OTM strike before the position turns profitable at expiration. Current CSTL IV rank near 6.40% sits in the lower third of its 1-year distribution, where IV often re-expands toward the mean; this favors premium-buying structures and disadvantages premium-selling structures on CSTL at 30.60%. As a Healthcare name, CSTL options can move on sector-level news flow (peer earnings, regulatory updates, industry-specific macro data) in addition to CSTL-specific events.
CSTL strangle positions are structurally neutral / high-volatility (long premium, OTM); the modeled P&L assumes European-style exercise at expiration and ignores early assignment, transaction costs, dividends paid before expiry on the stock leg (when present), and the bid-ask spread on the listed chain. CSTL positions also carry Healthcare sector concentration risk; news flow inside the sector (peer earnings, regulatory shifts, supply-chain headlines) can move CSTL alongside the broader basket even when CSTL-specific fundamentals are unchanged. Always rebuild the position from current CSTL chain quotes before placing a trade.
Frequently asked questions
- What is a strangle on CSTL?
- A strangle on CSTL is the strangle strategy applied to CSTL (stock). The strategy is structurally neutral / high-volatility (long premium, OTM): A long strangle buys an OTM call and an OTM put at offset strikes, cheaper than a straddle but requiring a larger underlying move to profit since both wings start out-of-the-money. With CSTL stock trading near $23.83, the strikes shown on this page are snapped to the nearest listed CSTL chain strike and the premiums come straight from the end-of-day bid/ask midpoint.
- How are CSTL strangle max profit and max loss calculated?
- Upside max profit is unbounded; downside max profit is bounded at the put strike minus the combined debit (reached at zero). Max loss equals the combined debit times 100 (reached anywhere between the two OTM strikes). Two breakevens at call-strike plus debit and put-strike minus debit. For the CSTL strangle priced from the end-of-day chain at a 30-day expiry (ATM IV 30.60%), the computed maximum profit is unbounded per contract and the computed maximum loss is unbounded per contract. Live intraday quotes will differ as the chain moves through the trading session.
- What is the breakeven for a CSTL strangle?
- The breakeven for the CSTL strangle priced on this page is no defined breakeven on the modeled curve at expiration, derived from end-of-day chain premiums. Breakeven is the underlying price at which the strategy's P&L crosses zero ignoring transaction costs and assignment risk. The current CSTL market-implied 1-standard-deviation expected move is approximately 8.77%; if the move sits well outside the breakeven distance, the structure's risk-reward becomes correspondingly tighter.
- When should you consider a strangle on CSTL?
- Strangles on CSTL are the cheaper cousin of the straddle - traders use them when they want a large directional move but are willing to give up the inner-strike sensitivity in exchange for a lower up-front debit on the CSTL chain.
- How does current CSTL implied volatility affect this strangle?
- CSTL ATM IV is at 30.60% with IV rank near 6.40%, which is on the low end of its 1-year range. Premium-buying structures (long call, long put, debit spreads) are relatively cheap in this regime; premium-selling structures collect less credit per unit risk.