Bernard J. Birkett
Senior Vice President, Chief Financial Officer at West Pharmaceutical Services
Thank you, Eric, and good morning. Let's review the numbers in more detail. We'll first look at Q2 2024 revenues and profits, where we saw a mid-single-digit decline in organic sales as well as declines in operating profit and diluted EPS compared to the second quarter of 2023, given the current market dynamics. I will take you through the drivers impacting sales and margin in the quarter as well as some balance sheet takeaways. And finally, we will provide an update to our 2024 guidance. First up, Q2. Our financial results are summarized on Slide nine, and the reconciliation of non- U.S. GAAP measures are described in Slides 17 to 22. We recorded net sales of $702.1 million, representing an organic sales decline of 5.9%.
Looking at Slide 10, proprietary products' organic net sales decreased 8.4% in the quarter as customers destocking continued at a higher rate than anticipated. High value products, which made up approximately 71% of proprietary product sales in the quarter declined by double-digits, primarily due to decreased sales of our Westar, Daikyo Crystal Zenith and FluroTec products.
Looking at the performance of the market units, the Biologics market experienced a mid-single-digit decline, primarily driven by lower volumes of Daikyo Crystal Zenith and Westar products. The pharma market units saw a low single-digit decline, primarily due to a reduction in sales of admin systems and Westar products, while the generics market unit declined double-digits, primarily due to lower volumes of our FluroTec and Westar products.
Despite these revenue declines in the quarter, we do expect revenues in the second half of 2024 to be greater than the first half. Our Contract Manufacturing segment experienced mid-single-digit net sales growth in the second quarter, led by growth in sales of components associated with injection-related devices. Our adjusted operating profit margin of 18% was a 650 basis point decrease from the same period last year. Finally, adjusted diluted EPS declined 28% for Q2. Excluding stock-based compensation tax benefit, EPS decreased by 28.4%. Now, let's review the drivers in both our revenue and profit performance.
On Slide 11, we show the contributions to organic sales decline in the quarter. Sales price increase has contributed $21 million or 2.8 percentage points of growth in the quarter. More than offsetting price was a negative volume and impact mix of $65.5 million, primarily due to lower sales volume caused by customer inventory management decisions in the period and a foreign currency headwind of approximately $6.1 million.
Looking at margin performance, Slide 12 shows our consolidated gross profit margin of 32.8% for Q2 2024, down from 38.7% in Q2 2023. Proprietary products' second quarter gross profit margin of 37% was 690 basis points lower than the margin achieved in the second quarter of 2023. The key drivers for the decline in the proprietary products' gross profit margin were lower production volume due to the reduced customer demand in the period and an unfavorable mix of products sold, partially offset by increased sales prices. Contract Manufacturing second quarter gross profit margin of 16.2% was 80 basis points greater than the margin achieved in the second quarter of 2023, primarily due to increased sales prices.
Now, let's look at our balance sheet and review how we've done in terms of generating cash for the business. On Slide 13, operating cash flow was $283.2 million for the six months ended June 2024, a decrease of $24.1 million compared to the same period last year, or a 7.8% decrease, primarily due to a decline in operating results, offset by favorable working capital management. Our second quarter 2024 year-to-date capital spending was $190.8 million, $33.3 million higher than the same period last year.
We continue to leverage our capex to increase both our high-value product and our contract manufacturing capacity. Working capital of approximately $849.3 million at June 30, 2024 decreased by $415.3 million from December 31, 2023, primarily due to a reduction in our cash balance. Our cash balance at June 30, 2024 of $446.2 million was $407.7 million lower than our December 2023 balance. The decrease in cash is primarily due to $454.1 million of share repurchases and our capital expenditures offset by cash from operations.
Turning to guidance, Slide 14 provides a high-level summary. We are updating our full-year 2024 net sales guidance to a range of $2.87 billion to $2.9 billion from a prior range of $3.0 billion to $3.025 billion. There is an estimated full-year 2024 headwind of approximately $5 million based on current foreign-exchange rates. We expect organic sales to decline approximately 1% to 2% compared to our prior guidance of 2% to 3% growth. We are updating our full-year 2024 adjusted diluted EPS guidance to be in a range of $6.35 to $6.65 compared to a prior range of $7.63 to $7.88.
Also, our capex guidance is expected to be $375 million for the year, which is an increase from the previous guidance of $350 million. The increase in capex is driven by additional investments in growth initiatives and the timing of spend on one of our major projects. There are some key elements I want to bring your attention to as you review our guidance. Full-year 2024 adjusted diluted EPS guidance range includes an estimated FX headwind of approximately $0.03 based on current foreign currency exchange rates, which is a decrease from the prior guidance of $0.04. The updated guidance also includes EPS of $0.22 associated with first half 2024 tax benefits from stock-based compensation. Our guidance excludes future tax benefits from stock-based compensation.
I would now like to turn the call back over to Eric.